Rehearsal Room Walls

I've been working on a rehearsal room project which is going into a community centre for local bands to use. I'm fairly satisfied that the room is sound proof (isolated walls, floating floor etc.). The last problem I have is decided on what type of materials to cover that walls with. At present the surface of the walls is plasterboard. I need something that is hard wearing (because local band might get a little carried away) and has a low burn factor. Since the space is going to be used as a rehearsal space and not a live room for recording the acoustics are not my number one concern. Also the budget is nearly gone so the cheaper the better. Thanks for any help you can give. Regards, Moog69