Wolf,
A school knows that it can only work together with parents. They cannot fight parents. Why would they think they can be successful or for that matter not detrimental when a parent proudly and loudly proclaims the opposite of what the school is trying to teach.
Besides, how much merit of his own can a child beginning school have yet? The school has to work with attitude. Will there be a positive attitude towards learning the lessons of the school and will lessons be reinforced in the home.
And we already see that *someone* has already determined that a parents actions should impact if they are accepted in school. See this brilliant thread.
http://www.theyeshivaworld.com/coffeeroom/topic/should-someone-who-is-considering-murder