The latest report from the New York City Charter Schools Evaluation Project compares the academic performance of charter school students with that of their peers who attempted to enroll in charter schools but were not selected in a random lottery. This method allows the researchers to isolate the effect of attending a charter school, without being concerned that factors related to the decision to apply to a charter school are really driving achievement differences.
The research team is led by Caroline Hoxby, an economist at Stanford University. These are the slides from her summary presentation at the Charter Center. Download the full report and technical materials at http://www.nber.org/~schools/charterschoolseval/.