or good training DVDs?

I am a middle school coach who was an ok jumper back in the day. All I know are the basics of the J run and the flop, and just drrilled the crap out of that, having them just keep jumping. While The 4 girls who I had were successful (all went from never having jumped to clearing 4'10"- 5'1").... I am looking for skill drills to help this years group with the different phases of jumping as I learned that tons of jumping every day can be harmful to the athletes. Plus, I don't want to use some unreputible persons drills/techniques

Thanks