Across schools, however, better pupils are assigned to slightly better teachers on average. The common practice of “tracking” pupils (filtering good ones into more advanced courses) could be to blame, the authors reckon, though they abstain from drawing firm conclusions. Whatever the cause, getting more effective teachers to instruct better-performing pupils naturally exacerbates the gap in achievement. Making the best teachers work with the worst pupils could go a long way toward minimising the yawning differences in attainment within a school system, the authors contend.
At the very least, that change would be lucrative for the pupils who benefit from it, according to the researchers’ second paper. They compare their measure of teacher quality against pupils’ fortunes as adults, after again controlling for pupils’ previous test scores and demography. (Pupils from the earliest years of their sample are now in their late 20s.) Unsurprisingly, exposure to better teachers is associated with an increased probability of attending university and, among pupils who go on to university, with attendance at better ones, as well as with higher earnings. Somewhat more unexpectedly, good teachers also seem to reduce odds of teenage pregnancy and raise participation in retirement-savings plans. Effects seem to be stronger for girls than for boys, and English teachers have a longer-lasting influence on their pupils’ futures than maths teachers.
The authors reckon that swapping a teacher at the bottom of the value-added spectrum with one of average quality raises the collective lifetime income of each class they teach by $1.4m. That rise would apply across all the teacher’s classes and over the whole of his or her career.
Measuring the Impacts of Teachers I: Evaluating Bias in Teacher Value-Added Estimates and Measuring the Impacts of Teachers II: Teacher Value-Added and Student Outcomes in Adulthood.