DYNAMIC TREATMENT EFFECTS OF TEACHER'S AIDES IN AN EXPERIMENT WITH MULTIPLE RANDOMIZATIONS
利用大规模两阶段随机实验数据，估计教师助手对学生成绩的动态平均处理效应，发现其提升成绩但主要惠及高社会经济地位和白人学生，成本效益分析显示其可替代缩小班级规模。
Using data from a large‐scale two‐stage experiment wherein students and teachers were randomized at both kindergarten entry and first grade to be sorted into classes either with or without full‐time teacher's aides, I estimate an econometric model that is uniquely suited to take advantage of this design to determine their effect on academic achievement. The identification strategy produces fully nonparametric dynamic average treatment effects for every treatment path. I find that the use of full‐time teacher's aides increases student achievement, but the benefits appear to accrue mostly to those of higher socioeconomic status and to White students. A cost‐benefit analysis shows that full‐time teacher's aides may be a competitive alternative to class size reductions in terms of net social benefits.