SMALL CLASSES ARE VERY popular with parents. Fewer kids in a room can mean more personal attention for their little ones. Teachers like them, too. Fewer kids means fewer tests to mark and fewer disruptions. Communities across the United States have invested enormously in smaller classes over the past 50 years. Pupil-teacher ratios declined from 22.3 in 1970 to 17.9 in 1985 and dropped to a low of 15.3 in 2008. But after the 2008 recession, local budget cuts forced class sizes to increase again, bumping the pupil-teacher ratio up to 16.1 in 2014, according to the most recent federal data available.
There’s a general consensus among education researchers that smaller classes are more effective. (In graduate school, I was taught that the benefits of small classes kick in once the class size falls below 16 students.) The benefits of small classes have become something of an informal yardstick. When I have written about unrelated educational reforms, researchers often compare them to the effectiveness of class-size reductions to give me a sense of their relative impact.