S.B.
I only had one kiddo (out of 6) that really had any acne. He was fairly young, too. The one thing we did that helped the most (other than simply having him wash his face with a mild soap morning and night) was increase his water intake. Seriously, it made a HUGE difference. For whatever reason, his skin is really sensitive to his water intake. After 10 days of increased water (12 oz 4 times a day), his acne was nearly gone. I can also tell when he doesn't drink enough - his face breaks out almost immediately.
Just a small thing that kids should be doing anyways and it might make a big difference :) Plus, it doesn't really cost anything!
Good luck!