High school teams follow AACCA regulations for tumbling and stunting.
www.aacca.org for rules
Your state or league may have more strict rules. Some states have rules about the routine format (i.e.: must have 3 jumps in the first 30 seconds, no tumbling in first 30 seconds etc.). Check with your state director on that.
Sidenote: it terrifies me that you've been coaching this team for 3 years and are just now asking what stunt are allowed at that level. Rules are not set in place to keep the competition a level playing field. Rules are put in place to keep the athletes safe at competitions, games and practices. The rules apply 100% of the time, not just if you're competing.