DC Voucher recipients have a 91% graduation rate versus 49% for DC public schools

In the article by Heritage Media Matters Tries but Fails to Refute the School Choice Evidence they show the effect of the DC voucher program. It sure seems like a voucher system would vastly improve education, but it gets fought every step of the way, and kids suffer for it. One of the things I found interesting was in the study, people who applied for the voucher, but didn't get it, had a 70% graduation rate. The reason seems to be that only parents actively involved in their child's education applied for the voucher, so parental involvement yields a 40% higher graduation rate. On one hand this is good, active parents can help counter-act the failings of public schools. But to focus on this misses the other hand, that their graduation rate was still more than 20% lower than the kids who used the voucher and went to private school. Evidently parental involvement can't totally overcome bad schools, bad teachers, bad environments.