Pre-Game Warm Up Time

[Sven]

This may be a game management issue, but help me out if you can. NFHS rules.

Home Team A takes the court approximately 20 minutes prior to game time and begins its pre-game routine. Timer starts clock countdown. (20 minutes) Team B comes out of locker room two minutes later and requests of Team A Athletic Director (management) that clock be reset to 20 minutes to allow them their full warm up time.

Denied.

What rulings apply here, if any?