You simply ask, if your polite about it, the worse they can do is say no. Although if they say yes they could lose their job and all their credibility  (meaning they can never be a cop again) best bet would be to just go buy a cop costume

Noooo, because thats a verrrry good way for that teacher to get fired. It may seem fine, but schools are very serious about no studen teacher relationships. Teachers can get fired for simply friending a student on facebook (if they get caught)