Our school did a night at the movies. Each class picked movie and performed a number of songs.

Main tip, is cull. As in, if the class is planning on doing 5 songs, make it 4 or even 3. I found the whole thing just way to long.

What I did like was that they go into someone to record the whole show. That way we could sit back and enjoy it, without having to worry about photos, video etc.