The importance of good teachers is no secret. Schools and their communities have always sought out the best teachers they could get in the belief that their students’ success depends on it.
But what we know instinctively still leaves some big questions, especially for those in charge of hiring, training and retaining a qualified teaching force. To begin with, how do you define a good teacher? What characteristics do you look for? Given all the factors related to student performance, how much impact can we expect from teachers? And finally, if teachers are so important to student learning, how can we make sure all students receive the benefit of good teachers?
In this overview, the Center looks at research that seeks to answer these questions.
Teacher quality counts
More than two decades of research findings are unequivocal about the connection between teacher quality and student learning. Indeed, What Matters Most: Teaching for America’s Future (1996), the influential report of the National Commission on Teaching and America’s Future, made teaching the core of its “three simple premises” in its blueprint for reforming the nation’s schools. They are:
- What teachers know and can do is the most important influence on what students learn.
- Recruiting, preparing, and retaining good teachers is the central strategy for improving our schools.
- School reform cannot succeed unless it focuses on creating the conditions under which teachers can teach and teach well.
Key teacher quality provisions of the No Child Left Behind Act (NCLB) underscore the importance of these premises. Central to NCLB’s goal of closing the achievement gap by 2014 is the requirement that all teachers be highly qualified by the end of the 2005-06 school year. For new teachers, this means that they must meet existing state certification requirements and demonstrate mastery of the content area in which they teach, either by passing a content knowledge test or by having majored in the subject in an undergraduate or graduate program.
Achieving this goal is proving to be a challenge for states and districts. The 2004 estimates put the number of teachers who have not yet met the highly qualified standard at 20 percent in elementary schools and 25 percent in secondary schools (U.S. Department of Education 2004).
Yet a growing body of research shows why current education policies emphasize teaching and why it’s important for states and districts to rise to this challenge. These studies not only provide insight into the characteristics of good teachers, they reveal how these contribute to student learning and closing achievement gaps.
Gauging the effect of teachers on student achievement
The most compelling evidence for the importance of teaching came initially from economists who adapted value-added models from business to measure the effect of teachers on student learning. While the statistical methods are complex, the definition of effective teaching is not. Simply, researchers looked for the change in students’ test scores according to the teacher they were assigned to. A highly effective teacher, therefore, is one whose students show the most gains from one year to the next. By using this approach, researchers are able to isolate the effect of the teacher from other factors related to student performance, for example, students’ prior academic record or school they attend.
Reports and data from two initiatives in Tennessee—the Tennessee Value Added Assessment System (TVAAS) and Student Teacher Achievement Ratio (STAR) project—and one in Texas—the University of Texas at Dallas Texas Schools Project—provide good starting points for understanding how much of an effect teachers have on student outcomes.
Insights from Tennessee and Texas
- The effect of teaching on student learning is greater than student ethnicity or family income, school attended by student, or class size.
- The effect is stronger for poor and/or minority students than for their more affluent and/or white peers, although all groups benefit from effective teachers.
- The effects accumulate over the years.
TVAAS was the first data-tracking system in the country to measure individual teacher performance according to annual gains in student test scores. Initiated in 1990, this system provides extensive data on state achievement tests for all students in grades 2-8 in Tennessee and allows for comparisons of teacher effects on students’ learning. Other states, such as North Carolina, Arizona, and Florida, have since adopted similar models; additional states are expected to follow suit.
The Tennessee Department of Education's STAR project was an experiment designed to evaluate the effects of smaller classes on student achievement over four years. The experiment randomly assigned students from various racial and socioeconomic backgrounds to small and regular-size classes in 79 schools across the state. STAR’s reliance on randomized samples, combined with the data-tracking capacity of TVAAS, offered an important and unique opportunity to examine variations in student achievement where the only difference between classes was the teacher.
Analyses of TVAAS and STAR data indicated that teachers had a substantial effect on student achievement. While the Tennessee data from STAR showed achievement gains associated with smaller class sizes, a stronger achievement gain is associated with teacher quality (Nye, Konstantopoulos and Hedges 2004). In addition, differences in student performance were more heavily influenced by the teacher than by student ethnicity or class, or by the school attended by the student.
The positive effects associated with being taught by a highly effective teacher, defined as a teacher whose average student score gain is in the top 25 percent, were stronger for poor and minority students than for their white and affluent counterparts. For example, one study of the Tennessee data found that low-income students were more likely to benefit from instruction by a highly effective teacher than were their more advantaged peers (Nye, Konstantopoulos, and Hedges 2004). Another study found that the achievement gains from having a highly effective teacher could be almost three times as large for African American students as for white students, even when comparing students who start with similar achievement levels (Sanders and Rivers 1996).
A second important finding from this work was that the positive effects of teacher quality appear to accumulate over the years. That is, students who were enrolled in a succession of classes taught by effective teachers demonstrated greater learning gains than did students who had the least effective teachers one after another. For example, fifth-grade math students who had three consecutive highly effective teachers scored between 52 and 54 percentile points ahead of students who had three consecutive teachers who were least effective, even though the math achievement of both groups of students was the same prior to entering second grade (Sanders and Rivers 1996).
Findings from the University of Texas at Dallas (UTD) Texas Schools Project lent additional credence to the Tennessee findings. This project gathered individual-level data on more than 10 million Texas students in grades K-12 from 1990 to 2002. By comparing the achievement of similar students within the same schools but assigned to different teachers, researchers were able to isolate the effects of the teacher on student achievement.
In their analysis of these data, Rivkin, Hanushek, and Kain (2005) found that teacher quality differences explained the largest portion of the variation in reading and math achievement. As in the Tennessee findings, Jordan, Mendro, and Weerasinghe (1997) found that the difference between students who had three consecutive highly effective teachers (again defined as those whose students showed the most improvement) and those who had three consecutive low-effect teachers (those with the least improvement) in the Dallas schools was 34 percentile points in reading achievement and 49 percentile points in math.
Characteristics of an effective teacher
The following teacher qualities are related to higher student achievement are:
- Content knowledge: Effective teachers have a solid background in the subject area they teach as measured by a college major or minor in the field.
- Teaching experience: Teaching experience, typically five years or more, produces higher student results. Some studies further suggest that the effect of inexperience can be a significant obstacle to student achievement.
- Teacher training and credentials: Certified teachers are more effective than uncertified, particularly in mathematics. In general, teachers with emergency certificates don’t perform as well as those with traditional certification. However, opinions conflict about the effectiveness of Teach for America (TFA) teachers, who enter classrooms with alternate certificates. Some comparative studies show larger gains by TFA teachers and others show fewer.
- Overall academic ability: Teachers with stronger academic skills perform better, whether these skills are measured by teachers’ SAT or ACT scores, grade point average or selectivity of the college they attended.
The Tennessee and Texas studies provide empirical evidence that teachers make a substantial difference in student achievement. But they are silent on the question of what characterizes an “effective teacher.” Other research helps pinpoint the dimensions of teacher quality. In the following sections, we review research findings on teacher characteristics that are commonly recognized measures of quality: Content knowledge, teaching experience, training and credentials, and overall academic ability.
Each of these measures shows a positive relationship to student performance. At the same time, the studies vary in their assessment of how strong an effect each dimension has on student outcomes.
Teachers’ knowledge of the content they teach is a consistently strong predictor of student performance, even though studies differ in how strong its effects are. This research typically uses teachers’ college degree to represent content knowledge.
- Minor in field. Darling-Hammond (1999) found that, although other factors had a stronger association with achievement, the presence of a teacher who did not have at least a minor in the subject matter that he or she taught accounted for about 20 percent of the variation in NAEP scores.
- Major in field. Goldhaber and Brewer (1996) found that the presence of teachers with at least a major in their subject area was the most reliable predictor of student achievement scores in math and science. They also found that, although advanced degrees in general were not associated with higher student achievement, an advanced degree that was specific to the subject area that a teacher taught was associated with higher achievement. In contrast, other studies did not indicate that teachers with graduate-level training in a content area performed better than did teachers having an undergraduate degree in their content area (Rivkin, Hanushek, and Kain 2005; Ferguson and Ladd 1996).
Research has also been consistent in finding positive correlations between years of teaching experience and higher student achievement. Teachers with more than five years in the classroom seem to be the most effective. Conversely, inexperience is shown to have a strong negative effect on student performance.
- Experienced teachers produce higher student test scores. A comprehensive analysis by Greenwald, Hedges, and Laine (1996) examined data from 60 studies and found a positive relationship between years of teacher experience and student test scores. Similarly, the UTD Texas Schools Project data showed that students of experienced teachers attained significantly higher levels of achievement than did students of new teachers (those with one to three years of experience) (Rivkin, Hanushek, and Kain 2005).
- Schools with more inexperienced teachers have higher drop-out rates. In a related finding, an analysis of math achievement and dropout rates in a sample of California high schools (Fetler 2001) found that schools whose dropout rates were in the highest 10 percent had 50 percent more new teachers than did schools in the lowest 10 percent.
Teacher training and credentials
There are several studies providing evidence that the students of certified teachers perform better than students of uncertified teachers.
- Certification in math produces better math scores. Fuller and Alexander’s (2004) analysis identified similar students who were taught by Texas math teachers who were also similar except that some were certified and others were not. The study found that the students taught by certified teachers scored better on the state math achievement test. A study that examined the math achievement of elementary students also found that students taught by new, uncertified teachers did significantly worse on achievement tests than did those taught by new, certified teachers (Laczko-Kerr and Berliner 2002).
- New or uncertified teachers have the least effect. Likewise, Darling-Hammond (1999) found a significant positive association between achievement and teacher certification. She also found a significant negative association between achievement and the presence of a high proportion of new or uncertified teachers in the school.
- Teachers on emergency certificates don’t perform as well as fully certified teachers. Fetler (1999) found that teachers with emergency teaching certificates did not perform as well as teachers who were fully certified, even when controlling for the amount of teaching experience.
The factor that sets certified teachers apart from other teachers is usually their training in teaching methods and in child and adolescent development, in addition to content knowledge. Because certification standards between states differ significantly, several researchers have sought to evaluate the effects of the teacher training that certification indicates. An analysis that synthesized findings from a group of studies showed that teachers with pedagogical training performed better than those who entered teaching without such training (Greenwald, Hedges, and Laine 1996).
Mixed reviews on alternate routes
Recently, studies have sought to evaluate the effects of teacher training by comparing teachers who take alternative routes to teaching with those who complete a traditional teacher preparation program. Alternative routes, which can take a number of different forms and which are growing in popularity, offer opportunities for people with an undergraduate degree in an area other than education to enter teaching and work toward certification while bypassing some of the education coursework that is required of college students getting their certification through a school of education.
- Conflicting research on Teach for America. One study of Teach for America (TFA)1 teachers in Houston found that TFA teachers had a positive effect on student achievement scores when compared with other new teachers (Raymond, Fletcher, and Luque 2001). Another analysis of the same data confirmed that students of TFA teachers did outperform those taught by other untrained teachers, especially in math; however, they did not perform as well as new teachers who had pedagogical training and certification (Darling-Hammond, Holtzman, Gatlin, and Heilig 2005).
- Little agreement on the balance of content knowledge and pedagogical training. Most of the research suggests that teachers who have had pedagogical training and who have received certification produce better student achievement scores than those who have not, although some studies dispute this finding (Goldhaber and Brewer 2000). Together, these studies have touched off a debate over the optimal balance between content and pedagogical knowledge (see, for example, Goldhaber Brewer 2000; Darling-Hammond, Berry, and Thoreson 2001).
Criticisms of teacher training and licensing procedures stem largely from a belief that the requirements for certification do not encompass all the characteristics that should be sought in teachers and thus should be reformed to require more content knowledge and displays of teaching competency (Walsh and Snyder 2004). While different certification requirements in different states make generalizing about the research difficult (Hanushek, Rivkin, and Taylor 1996), most research does show a positive connection between the training required for certification and student achievement.
Overall academic ability
There is research that has shown that students of teachers who have greater academic ability—be it measured through SAT or ACT scores, GPA, IQ, tests of verbal ability, or selectivity of the college attended—perform better. As mentioned earlier, the one exception where the evidence is mixed occurs in studies that used the attainment of advanced degrees as a proxy for academic ability. Most of the research on these traits is old (see Darling-Hammond 1999 for a summary), but more recent studies support these results.
- Teachers’ verbal ability counts. Greenwald, Hedges, and Laine’s (1996) analysis showed an overall positive relationship between a teacher’s verbal ability and student performance.
- Teachers with high ACT scores produce better readers. A study of teachers in Alabama by Ferguson and Ladd (1996) found a correlation between a teacher’s higher ACT scores and higher reading scores for her students. But the researchers found no significant difference for math scores.
How does teacher quality affect the achievement gap?
Regardless of how it’s measured, teacher quality is not distributed equitably across schools and districts. Poor and minority students are much less likely to get well-qualified teachers than students who are better off.
- The Tennessee studies revealed that African American students were almost twice as likely to be taught by the least effective teachers (Sanders and Rivers 1996).
- Data from the U.S. Department of Education’s national Schools and Staffing Survey (SASS) showed that students in high-poverty secondary schools were 77 percent more likely to be taught by teachers without degrees in the subject they were teaching than were their affluent counterparts. Students in high-minority schools were 40 percent more likely to be taught by out-of-field teachers. The problem is especially acute in middle schools (Jerald and Ingersoll 2002).
- Poor and minority students are about twice as likely to have teachers with less than three years of teaching experience (National Center for Education Statistics 2000).
- Districts that are predominantly poor or minority were considerably more likely to employ uncertified teachers (Darling-Hammond 1999).
- Teacher mobility is a much greater problem for poor and minority students; teachers are much more likely to move from urban to suburban schools than vice versa (Hanushek, Kain, and Rivkin 2004).
The distribution of teachers with these qualities has grown more inequitable in recent years. Jerald and Ingersoll (2002) showed that the problem of out-of-field teachers actually got worse for disadvantaged students during the 1990s. In addition, some states’ efforts to reduce class size—and in so doing creating a need to increase the teacher workforce—have led to the hiring of more unqualified and untrained teachers, thus minimizing the possible benefits of lower class sizes (Jepsen and Rivkin 2002).
The impending teacher shortage, estimated at more than two million teachers by 2007 (Ingersoll 2003), could exacerbate the inequitable distribution of teacher quality in the coming decades unless policymakers and educational leaders find ways of increasing the supply of skilled teachers and ensuring that the lowest performing students are enrolled in their classes.
Implications for closing the achievement gap
Research consistently shows that teacher quality—whether measured by content knowledge, experience, training and credentials, or general intellectual skills—is strongly related to student achievement: Simply, skilled teachers produce better student results. Many researchers and analysts argue that the fact that poor and minority students are the least likely to have qualified teachers is itself a major contributor to the achievement gap. It follows that assigning experienced, qualified teachers to low-performing schools and students is likely to pay off in better performance and narrowing gaps.
This is sometimes easier said than done. Some attempts to redistribute good teachers to low-performing schools have not been entirely successful. The most common strategy has been to offer pay increases or signing bonuses for teachers to come to high-need areas or to teach high-need subjects. Massachusetts, for example, offered a $20,000 signing bonus to attract qualified candidates into the teaching profession. Yet even when the incentives were substantial, teachers have not always been willing to go to or to stay in difficult schools. Major drawbacks to these efforts were: (1) not enough attention to what was needed to retain teachers, and (2) too much attention to individuals and too little on schools (Liu, Johnson, and Peske 2003).
What these results mean is that incentives to work in hard-to-staff schools should also take into account the working conditions they provide for teachers. For example, low-performing schools often have weak organizational supports for teachers. Often they do not have a culture of high expectations for students and teachers or that values teacher learning, collegiality, and cooperation. Districts also need strategies to ensure that these schools have strong and resourceful principals and that teachers have sustained professional learning opportunities, including intensive long-term new teacher-induction programs, in which they can work with colleague to continually sharpen and upgrade their knowledge and skills. (see high-performing, high-poverty schools )
Toward a highly qualified teacher in every classroom
This research also suggests that scattering a handful of good teachers around the district is not going to produce wide-ranging results. One study has identified a teacher quality “tipping point” when the proportion of underqualified teachers is about 20 percent of the total school faculty. Beyond this point, schools no longer have the ability to improve student achievement (Shields, Esch, Humphrey, Young, Gaston, and Hunt 1999). Clearly, districts need to recruit, develop, and retain a well-qualified teaching force.
Questions still remain for research to answer. Most of the effective teacher studies, for example, have focused on elementary school. While a few studies suggest that the teaching effect is somewhat less in high school, a lot more needs to be discovered before we can make that statement with confidence. In addition, the conflicting findings on the effectiveness of alternate route teachers need to be resolved, especially since many districts rely on such non-traditional candidates to deal with teacher shortages. We also need to know more about the incentives and working conditions that will attract highly effective teachers to traditionally hard-to-staff schools.
But as this review has shown, there is already enough evidence to show unequivocally that good teachers are vital to raising student achievement and closing achievement gaps. The challenge for districts is to ensure that every classroom is staffed by a skilled, qualified teacher.
There are a number of actions to take:
- Districts can step up recruitment efforts to hire teacher candidates who have strong academic credentials and who have completed a rigorous teacher preparation program.
- District recruiters could assess the rigor of teacher preparation programs by closely examining transcripts and other records that identify and describe the actual courses that teacher candidates have taken in order to be certified. This information could prompt K–16 discussions between districts and institutions of higher education regarding ways to ensure that teacher preparation programs explicitly address the districts’ needs.
- States and districts can also collaborate with higher education to target and recruit top candidates to enter teaching. K–16 partnerships can further help address areas of shortage through dual enrollment agreements, faculty sharing and distance learning opportunities.
- For newly hired teachers, districts can establish and maintain intensive, long-term induction programs that focus on helping new teachers meet challenging professional performance standards.
States and districts can also explore value-added methods for monitoring teacher effectiveness, such as those used in Texas, North Carolina and other states. This data helps inform decisions about where to assign teachers, how to staff schools, and what supports and professional development opportunities are needed in order to maximize the benefits of the most valuable academic resource, teachers.
The Center for Public Education will continue to monitor state and district efforts to provide each child with a highly qualified, effective teacher.
This document was prepared by Policy Studies Associates (PSA). PSA, based in Washington, D.C, is a research and evaluation consulting firm specializing in education and youth development. Its clients include federal, state, and local government agencies, foundations, and other organizations.
Posted: November 1, 2005
© 2005 The Center for Public Education
Teach for America (TFA) is an AmeriCorps program that places recent college graduates in teaching positions in high-need districts throughout the country. Participants typically do not have education backgrounds and receive a brief training and induction period before beginning their teaching assignments. It should be noted, however, that TFA is highly competitive and often attracts students from top universities.