the rule which applies to the original post is:

KSHSAA Handbook Rule 22 (page 34): "Outside Competition" This rule applies to students in grades 7-12.

From Labor Day through the Friday before Memorial Day a student who is a member of his school team may NOT compete as a member of an outside team or as an independent competitor in outside competition in the same sport.

A student becomes a member of a school team when he/she first participates in a practice session.