Sorry to hear that. Life is to short to waste your time with a lousy teacher. Better to find a really good teacher in some other art than to continue as you are IMHO. Considering what you describe I would wonder about the quality of what you are being taught.

Is there anyone in your class who's very good at 'taking' the crazy teenagers' techniques without getting hurt? Does the teacher ever practice with them himself? Learning to take techniques safely is IMO part of the training and you should be getting gradually taught how to do it better and better, maybe from your teacher directly or from students senior to you.

Falls, definitely -- even if you're doing them better than others in the class you can always get better. And there are a lot of different ways of falling that can be useful in different situations. Also moving with pressure instead of against it, 'escaping' at times, etc. Being in good shape physically, with strong and flexible joints and being able to move lightly and quickly. And if you have anything that's already injured and not healed that part will make you more vulnerable. Those things are important even when the technique is being done right, but they will all be what makes you more likely to save yourself when something goes wrong, too.

There are lots of things you can do to get better at protecting yourself, they're just not 100% though in every situation, that's all I'm saying. You still need partners who are doing their part to be safe too.