A couple of things to add...
I found that having an answer key on the practice problem sheets is a real plus. It provides immediate feedback to the student that he is learning and accomplishing. If he doesn't solve the problem correctly he can immediately ask me or another student for help...
Background to how this material was used. The school I taught in was a working-class suburb. Students ranged from average to an occasional brilliant student. Most years I had a few exchange students from foreign countries who were always excellent. The biggest difference from most schools was...
I'm a retired physics teacher who taught physics and AP physics for maybe 40 years. I saved my problem sheets and tests. If you are a beginning (or experienced) teacher and need pre-made problems and tests I'll send you mine. I'll wait a few months for a reply, then to the dumpster they go...