Use of off air TV programs in class/ out of class copyright?

My mom’s been sending me children’s TV shows from the states for my daughter (Pioneer DVD recorder, pretty neat).

I’ve showed some my students some of them. They especially like the Power Rangers.

Anyway, what are the rules? I’ve read that teachers can show any program from off air TV but they must delete the show within 45 days. I

This is a grey area. If you can prove your using the material for education then it should be ok.