"For HS, I think 15 minutes is too short (Most USAW matches are 1 minute rounds, plus kids have an unlimited supply of energy that I wish I could borrow). 30 minutes seems about right."

USAW uses 15 minutes for all ages, including Cadets and Junior (HS age) which are 6 minutes matches just like in high school. I'm with you that 30 minutes might be a good compromise or we just leave it like it is. It doesn't come up as an issue too much. Mostly at scrambles.