IFAB changed this a while ago ... stating that straight red for DOGSO was too harsh ... essentially a triple punishment ... player removal, pk, and one game suspension. Ref can still issue a straight Red for excessive, deliberate, etc. foul but a normal foul in a DOGSO situation calls for a YC.
Here's an excerpt from NFHS on new rules for this year:
Soccer Rules Changes - 2018-19
By NFHS on February 20, 2018
12-8-1f, 15 (NEW): 1. A player, coach or bench personnel shall be cautioned (yellow card) for:
...3. a player commits a foul, outside the penalty area, attempting to deny an obvious goal-scoring opportunity, and the goal is not scored; or 4. a player commits a foul, inside the penalty area, while not attempting to play the ball, and the goal is not scored.
Assuming KHSAA is following NFHS (and I think they do) ... I'd agree with Mex on this one.