More on Charter Schools

Charter schools are publicly funded but operate outside the regulatory
framework and collective bargaining agreements characteristic of
traditional public schools. In return for this freedom, charter schools
are subject to heightened accountability. This paper estimates the
impact of charter school attendance on student achievement using data
from Boston, where charter schools enroll a growing share of students.
We also evaluate an alternative to the charter model, Boston's pilot
schools. These schools have some of the independence of charter
schools, but operate within the school district, face little risk of
closure, and are covered by many of same collective bargaining
provisions as traditional public schools. Estimates using student
assignment lotteries show large and significant test score gains for
charter lottery winners in middle and high school. In contrast,
lottery-based estimates for pilot schools are small and mostly
insignificant. The large positive lottery-based estimates for charter
schools are similar to estimates constructed using statistical controls
in the same sample, but larger than those using statistical controls in
a wider sample of schools. The latter are still substantial, however.
The estimates for pilot schools are smaller and more variable than
those for charters, with some significant negative effects.

Did the authors control for other factors and parse the statistics carefully?  One of the authors is Joshua Angrist, nuff said.