Measuring Teacher Quality
Thursday, December 4th, 2008 By Matthew CarrThe Brookings Institution has a new study out on identifying teacher effectiveness in the classroom. As we noted in our recent report on merit pay, and as has been noted by others, teacher quality is the single most important determinant of student success or failure that is within the control of schools. The Brookings study examines ways to distinguish high and low quality teachers. They find that the test scores of a particular teacher’s students (value-added, not absolute) in the previous two years is an efficient indicator. Whether a teacher is certified, however, is not.
While certification status was not very helpful in predicting teacher impacts on student performance, teachers’ rankings during their first two years of teaching does provide a lot of information about their likely impact during their third year. The average student assigned to a teacher who was in the bottom quartile during his or her first two years lost on average 5 percentile points relative to students with similar baseline scores and demographics.
In contrast, the average student assigned to a top-quartile teacher gained 5 percentile points relative to students with similar baseline scores and demographics. Therefore, the average difference between being assigned a top-quartile or a bottom-quartile teacher is 10 percentile points.
For some, this may all seem rather intuitive. But the education establishment has largely fought hard against the use of test scores as an evaluation measure for teachers. Studies like this one clearly show the fallacy of schools avoiding the most accurate predictor of a teacher’s future performance (which is to say outcome, not input, measures) when conducting evaluations.
Finally, the report’s policy recommendations are salient and well worth being part of any reform debates in Ohio.
Recommendation 1: Reduce the barriers to entry into teaching for those without traditional teacher certification.
Recommendation 2: Make it harder to promote the least effective teachers to tenured positions.
Recommendation 3: Provide bonuses to highly effective teachers willing to teach in schools with a high proportion of low-income students.
Recommendation 4: Evaluate individual teachers using various measures of teacher performance on the job. There is no consensus yet on the one best way to evaluate teacher performance, so many measures of teacher performance might be used, such as principal evaluations, parent evaluations, classroom observations, and the number of times a teacher is absent. However, measures of outputs and performance rather than credentials would need to be used. Moreover, some measure of “value-added,” or the average gain in performance for students assigned to each teacher, would need to be a significant component of that scale. That requirement leads to our last recommendation.
Recommendation 5: Provide federal grants to help states that link student performance with the effectiveness of individual teachers over time.
