[nonother]

From the coach's manual:

The Students
Your FVC team will have up to 10 students, typically high school aged. For a true team experience, we recommend a minimum of three students per team. Students come to the team from many different avenues such as schools, after-school programs, home-school groups, Girl Scouts, Boy Scouts, Girls Inc., Boys & Girls Clubs, YWCA, YMCA, Big Brothers-Big Sisters, religious groups, and neighborhood groups.

-----------
So I don't think it's a rule, but it's definetly a guideline. I know for a fact some middle schools have teams. As far as students that have graduated from high school, I have a feeling they are not allowed...but I'm not sure if that's an official rule.