if its the instructors plane then its the instructors fault. the instructor needs to make sure his plane is in top notch condition. also as an instructor, you should be able to tell if the student is getting himself into trouble. You have the switch, you are in control. I have never had a students plane crash when i am instructing. If the student was practicing landings, obviously they wernt ready to be landing and you pushed them a little too far that day. give us more details of what happened. The student should help you repair it though, just out of common courtesy.

sean