What do I do if I fall off on a school ski trip?

If you are skiing with a school, there will be instructors there. One instructor typically goes first and one instructor goes last. If you fall off, the instructor will see that you've fallen off and he will get off the lift and ski back down the mountain with you. There's no way to fall off of a chairlift, except when you are getting on/off, but if you're really worried about that, tell your ski instructor and he/she will help you. They might even tell the person operating the lift to slow it down for you. Don't worry, people understand that you might be nervous and they will help you.