Totally ridiculous. Dd6's school has >600 student, ds9 1200 or so. Parents are encouraged to volunteer, to come and eat lunch with their kids, etc. I think there would be a major revolt if a principal tried to institute a rule that parents could not have access to the building. Even with greater security etc. there are ways to make it work. Totally a school culture thing and it sounds like the principal is crazy. How do you get to be a principal never having been a classroom teacher? That is just unbelievable to me.