In 1990 Wisconsin began providing vouchers to a small number of low-income students to attend nonsectarian private schools. Controlling for individual fixedeffects, I compare the test scores of students selected to attend a participating private school with those of unsuccessful applicants and other students from the Milwaukee public schools. I find that students in the Milwaukee Parental Choice Program had faster math score gains than, but similar reading score gains to, the comparison groups. The results appear robust to data imputations and sample attrition, although these deficiencies of the data should be kept in mind when interpreting the results.

We develop a model of optimal schooling investments and estimate it using new data on approximately 700 identical twins. We estimate an average return to schooling of 9 percent for identical twins, but estimated returns appear to be slightly higher for less able individuals. Simple cross-section estimates are marginally upward biased. These empirical results imply that abler individuals attain more schooling because they face lower marginal costs of schooling, not because of higher marginal benefits.