I suspect he doesn't actually do it, because at that level of school, one of the products parents are buying is the transition of their child to a decent university, if he does anything to hamper that most will take the £34,500 and their offspring elsewhere.
It may be that he has several parents who don't want their child to have a relationship in case it messes up their school work which might mess up their university application which would mess up many of those parents projected path for their teen.
I am sure someone can come along and defend the school but I am not sure that he is the sort of person I would want directing my child's time at school