The Impact of Teacher Effectiveness on Student Achievement

Impact of Teacher Effectiveness on Student Achievement

The work of Bill Sanders, formerly at the University of Tennessee’s Value-Added Research and Assessment Center, has been pivotal in reasserting the importance of the individual teacher on student learning.4  One aspect of his research has been the additive or cumulative effect of teacher effectiveness on student achievement. Over a multi-year period, Sanders focused on what happened to students whose teachers produced high achievement versus those whose teachers produced low achievement results. He discovered that when children, beginning in 3rd grade, were placed with three high-performing teachers in a row, they scored on average at the 96th percentile on Tennessee’s statewide mathematics assessment at the end of 5th grade. When children with comparable achievement histories starting in 3rd grade were placed with three low-performing teachers in a row, their average score on the same mathematics assessment was at the 44th percentile, an enormous 52-percentile point difference for children who presumably had comparable abilities and skills. Elaborating on this body of research, Dr. Sanders and colleagues reported the following:

. . . the results of this study well document that the most important factor affecting student learning is the teacher. In addition, the results show wide variation in effectiveness among teachers. The immediate and clear implication of this finding is that seemingly more can be done to improve education by improving the effectiveness of teachers than by any other single factor. Effective teachers appear to be effective with students of all achievement levels, regardless of the level of heterogeneity in their classrooms.

Further analysis of the Tennessee data indicated that the effects on achievement of both strong and weak teachers persisted over three years: subsequent achievement was enhanced or limited by the experiences in the classrooms of strong or weak teachers, respectively. In other words, learning gains realized by students during a year in the classroom of an effective teacher were sustained over later years and were compounded by additional years with effective teachers. Conversely, depressed achievement results resisted improvement even after a student was placed with an effective teacher, and the negative impact was discernible statistically for approximately three subsequent years. Given results like these, it’s no wonder that the researchers found that “a major conclusion is that teachers make a difference.”

In a comparable study by researchers in Dallas, Texas, similar results were found in both math and reading during the early grades. When 1st grade students were fortunate enough to be placed with three high-performing teachers in a row, their average performance on the math section of the Iowa Tests of Basic Skills increased from the 63rd percentile to the 87th, in contrast to their peers with similar scores whose performance decreased from the 58th percentile to the 40th, a percentile difference of 42 points. A similar analysis in reading found a percentile difference of 44 percentile points. The studies in Tennessee and Texas produced strikingly similar findings: Highly effective teachers are able to produce much greater gains in student achievement than their less effective counterparts.

While the numbers help to summarize the cumulative academic effects of less effective teachers, we can only imagine the sense of failure and hopelessness that these children and their parents experienced during the years in these classrooms. Undoubtedly, the children wondered what was wrong with them when, in reality, it was the quality of their instruction. A common yet misguided bit of folk wisdom has been that adversity, in the guise of an ineffective teacher, builds character and that a student can catch up the following year. The research indicates otherwise.

Based on the findings from the Dallas Public Schools’ Accountability System, the negative effects of a poor-performing teacher on student achievement persist through three years of high-performing teachers. The good news is that if students have a high-performing teacher one year, they will enjoy the advantage of that good teaching in future years. Conversely, if students have a low-performing teacher, they simply will not outgrow the negative effects of lost learning opportunities for years to come. Further exacerbating the negative effects of poor-performing teachers, the Dallas research shows that “lower-achieving students are more likely to be put with lower effectiveness teachers . . . . Thus, the negative effects of less effective teachers are being visited on students who probably need the most help.”

Summarizing the findings from studies of the Dallas and Tennessee Value-Added Assessment Systems, Mendro states:

Research . . . has demonstrated the effects of teachers on student achievement. They [the researchers] show that there are large additional components in the longitudinal effects of teachers, that these effects are much larger than expected, and that the least effective teachers have a long-term influence on student achievement that is not fully remediated for up to three years later.

In straightforward terms, these residual effects studies make it clear that not only does teacher quality matter when it comes to how much students learn, but also that, for better or worse, a teacher’s effectiveness stays with students for years to come.


Linking Teacher Evaluation and Student Learning by Pamela D. Tucker and James H. Stronge