I can't speak for all districts but I can say that is not how it works in our school.
I can assure you that your district follows KSHSAA rules and your coach, athletic administration and local BOE are well aware they have absolutely NO control over an athlete prior to their participation in a high school activity.
Plus, our team has special exercises for those who miss practice regardless of the reason. Those that have seen or done the those exercises tend not to want to miss a practice.
I am not certain this situation would pass the legal litmus test, and if the administration would allow this discipline if the matter is pressed.
I would be very hesitant to punish an athlete for participating in an activity prior to participation in the high school activity. If the athlete misses practices after choosing to participate with the high school that is another matter entirely.