If I were to teach weight training at a high school, I always had one assignment in mind. I would want the students to record themselves doing a certain exercise. This is a good idea because it shows to yourself what your are doing right or wrong. You can analyze your video to see if your reps are consistent. It would be easier to teach if I can show the student what he or she is doing wrong when he or she has an example they can see for themselves.

This would be the kind of video I would be expecting, I made this video  and I noticed that I made some mistakes too. Another assignment you can do for this is to look up videos of a professional lifter and see how his or her reps look.