For the last few years it has been a lot of fun preparing younger athletes for sporting seasons. One athlete that I have been working with since 7th grade has really come a long ways toward complete athletic development.
Starting Slow
Starting out there was really no point in putting a bunch of external load and just hoping that he would get stronger. There was a lot of time spent at Very modest weights and adjusting form and building up his Kinesthetic awareness and Proprioception.
There was one exercises that I really loaded him up on and that was the sled push. This was physically demanding as well as mentally. This was also a great way to develop lower body strength with out having to much time spent on form and positioning. If you get in the push position on a sled your body almost lines up itself automatically which I feel makes this one of the most useful moves when developing some sick lower body strength while teaching the more form intensive movements.
Now as a freshman we are still working on basic movement patterns, never losing form, and never getting to specific at such a young age.
Two ways in which I like to teach Explosiveness to younger guys is utilize the hang clean. Along with this on a different day I will usually include an unloaded explosive movement which would be a wide array of box jumps, broad jumps, and other various body weight jumps.
Once developing a solid base of strength and reinforcing technique the loading of the movements began. Here is couple of movements we used and are sticking to for a while. Here are a couple of his warm-up sets on a Front Squat and 1 leg RDL and for upper body loaded push ups.
Pretty much everything we do stops once form is compromised. Does this mean he doesn't load up and lift heavy...Hell No! He benches more than anyone in his grade, loves to pull some heavy Hex bar Deads, and rep out some heavy chins as well. The only difference between him and most other younger athletes he developed a solid base of movement through a multitude of dynamic drills. He also took the time to LEARN the specific movements before he blindly threw on too much weight and failed. But, one of the biggest keys is progressive overload. At this age if you build them up slowly, even if it's adding 2.5# weights per week, this adds up to some serious weight over the course of a year. People just have to realize that when working with younger athletes it is a long term plan to athletic development not a head start on pressing more weight.