Fade-out, Teacher Quality, and Summer Learning Loss
By Bryan Caplan
Getting students to learn is hard. One of teachers’ favorite consolations, though, is that “If I can just get through to these kids, it will all be worth it.” The hope, apparently, is that successful teaching will permanently changes students’ lives. But does it? A new paper by Jacob, Lefgren, and Sims (ungated version here) rains on educators’ parade. High-quality teachers do change their students more, but they can’t stop fade-out:
The primary claim of the recent teacher value-added literature is that teacher quality matters a great deal for student achievement… While this claim may well be true relative to other policy alternatives, our results indicate that contemporaneous value-added measures are a poor indicator of long-term value-added. Indeed, test score variation due to teacher value added is only about one-fifth as persistent as true long-run knowledge and perhaps one-third as persistent as the overall variation in test scores. Thus when measured against intuitive benchmarks, contemporary teacher value-added measures almost certainly overstate the ability of teachers, even exceptional ones, to influence the ultimate level of student knowledge.
…Taken at face value, our results for two-year persistence imply that a policy intervention to raise teacher value-added by a standard deviation would produce along-run effect on student math achievement closer to 0.02 standard deviations than the 0.10 standard deviation increase found in the literature.
Which reminds me: Advocates of year-round school (and even worse, Saturday school) often argue that summer learning loss is large. But notice: Summer learning loss is just a specific kind of fadeout! Unless a high school diploma magically locks in knowledge, anyone who believes in severe summer learning loss should also expect kids in year-round or Saturday school to quickly lose their extra knowledge after graduation. Strange as it may seem, then, summer learning loss is an argument for less education. Why make the poor kids suffer if they won’t retain what they learn anyway?