Experimental estimates of education production functions

This paper analyzes data on 11,600 students and their teachers who were ran domly assigned to different size classes from kindergarten through third gr ade. Statistical methods are used to adjust for nonrandom attrition and tra nsitions between classes. The main conclusions are (1) on average, performa nce on standardized tests increases by four percentile points the first yea r students attend small classes; (2) the test score advantage of students i n small classes expands by about one percentile point per year in subsequen t years; (3) teacher aides and measured teacher characteristics have little effect; (4) class size has a larger effect for minority students and those on free lunch; (5) Hawthorne effects were unlikely.