It is a dystopian setting, because the world had fallen to a point where kids who don't do well in school, can have their rights taken away, and effectively turned into slaves.
I mean, since 'happy' is relative, one 'happy' ending could be the girls losing their rights and having to be his servants. Another is that he is successful, and they all work for him in various ways, like some work in the school as helpers, teachers, and so on, others work in his house, cleaning, cooking, and what not, and so on... But I guess someone might consider it 'happy' if the girls all pass and the HM and the people backing him go to jail, so who knows?