My information is very old, but I was a math instructor at CTY in Lancaster, PA in the late 80's. We didn't assign specific homework back then, but since everything was self-paced study anyway, some kids would do more work in the evenings for fun and turn it in the next day. I have no idea how they handle it now, though. (My guess is that they have instructors with a lot more credentials than I had, too, but I have no direct knowledge.)