If you don’t have a high regard for the Harvard CS curriculum, it’s reasonable enough to disqualify people on that basis.

That said, I think you’re completely out of touch with how 18 year olds choose universities. It can be as simple as a friend of theirs is also attending, or the school is close to a parent’s home, or they were actually in a liberal arts program before they switched into CS.

Sometimes as you implied, it’s their parents making that decision for them.

There’s no point in holding the cost of a student’s education over them, especially as you don’t know even how much they paid.