Not exactly sure what you mean, i would say 95-98% of competitors are 18 or younger when they graduate. Here is an exert from the KSHSAA Guidelines:
A student who reaches nineteen on or before September 1, will be ineligible for athletics. Contact Gary Howard, Athletic Director, if you fall into this category to explore waiver options. Any student who reaches nineteen after September 1, will be eligible for the remainder of the school year.

I really don't thing this is ever an issue. Could be worse, you could have had to compete against the 21 year old Amobi Okoye, starting defensive tackle for the Houston Texans.