Private Schools and Public School Achievement
以伊利诺伊州学区数据，将私立学校学生比例作为内生变量，用天主教宗教变量识别两阶段模型，发现私立学校对公立学校学业成就无直接影响。
The effects of private schools on public elementary and secondary school achievement in Illinois are estimated. The percentage of students in private schools in a school district is treated as an endogenous variable in the achievement equation. Catholic religion is used to identify a two-stage model. It is shown that private schools have no direct effect on public school achievement.