School A and School B

Imagine two schools serving the same grade levels in the same community. School A and School B, such that:

• School B has a school day two hours longer than School A.
• School B has a school year two weeks longer than School A.
• All students in the community can automatically attend School A, under any circumstances.
• Students must explicitly apply to School B at the beginning of the single entry year of School B. If more students apply to School B than there are places, students are selected by lottery.
• Students always have the right to leave School B to attend School A, but not vice versa.
• School B reserves the right to replace, or not replace, students who leave School B.

Outside of the context of the contemporary US charter debate, I don't think anyone would argue that School A and School B would contain equivalent populations of students, just based on the above rules. This is a trivial prediction.

The interesting question is how did we get to the point where this would be a controversial assertion?