Here's a drill you can do with broccoli. Tape some broccoli to your hands and feet and then do some punches and kicks to your opponent's face. Your opponent will do just about anything to avoid getting broccoli anywhere near their mouth that they will be able to block or evade every punch and kick you throw at them which will improve their defenses.
What sort of karate are they doing then that these people get bored? I've been lots of things in a session but never, ever bored. I'm suspecting that it's poor instructing or that these people are going to McDojos.