How else are we expected to believe that parents are not getting their kids out of this school ASAP? Not every single of the boys and girls is an orphan or a street urchin, huh?
Let's not forget that the owner of the Mega Corp. financing the school is said to be perfectly willing and able to destroy the lives of anyone who won't go along with his plans.
A single phone call to the police or whatever Japan calls their equivalent of the FBI would have a serious investigation called in, Mega Corp. or no. The school would be shut down, and the CEO would be put on trial for unethical experimentation, and even if he won, it wouldn't be a stretch to think the girl's families or a Screw the Rules, I'm Doing What's Right! type might lynch him.