Limit instructors to the demand, or as many as you can manage.
Require the student to fill out a dive log for every dive, 1 paragraph. Depth, time, passage, etc. Write what happened, what THEY did wrong, how they will fix it. It would make a great record for the student as well. Would be good for records for the instructor for insurance, and the agency could see what's going on. Sure, you could lie, but very few students would be down to lie on a course they're paying for about short cutting skills.
For basic cave, video valve drills, s drills, lost line w/ blacked out mask, on line exits, etc. UW cameras can be had less then the cost of 1 students tuition, mail in a $0.50 cd that teh agencies can randomly review. Doesn't have to be professional quality, just show the student what he/she did wrong, and show the agency that drills were done.