Ultimately the schools are there to serve the people, so if the people want arguments over things like whether to teach sex ed then isn't that their prerogative

Ultimately the schools are there to serve the people, so if the people want arguments over things like whether to teach sex ed then isn't that their prerogative? I know it's a problem and I don't agree with some sides of that argument myself... but in a democracy aren't these issues supposed to be devolved to the demos? Isn't that the whole point? Do the teachers 'know better'? Who's determining who knows better?