I didn't reply to the others because I didn't want to get into a whole fight about it. But the OP's original message about selection-bias is still correct. The

I didn't reply to the others because I didn't want to get into a whole fight about it. But the OP's original message about selection-bias is still correct. The article's original claim is that charter schools does work for disadvantage and black students. But that is NOT what the data supports. The data supports that it works for disadvantaged and black students who have active parents. That conclusion raises more questions than it answers. I think your theory makes a lot of sense. Thank you for sharing that.