We didn't quite pull this off but almost (only last year) ......

He was one of those teachers who never has any control and we did loads of little tricks and stuff, but one time we were going to all sit in complete silence and stare at him. We weren't going to talk or answer questions or do anything, just all sit completely still and in complete silence and stare. That would've been great as he was used to us lobbing blu-tack across the room etc.
Didn't quite work though - just never got sorted properly.

xLx