Why are we okay with content filtering in schools? In Poland where I live, parental control basically doesn't exist. Children routinely watch movies, play game

Why are we okay with content filtering in schools? In Poland where I live, parental control basically doesn't exist. Children routinely watch movies, play games and visit websites that they're theoretically not supposed to visit. Parents know about it and don't really see an issue with it. I've seen several boarding school networks, none of them had any filtering whatsoever. The only filters I've seen were on computers in IT classrooms, but nobody uses those for non class-related activities anyway. As far as I know, we don't even have a law banning selling x-rated content to minors.