i dont think your situation is unique at all. every parent group i have ever known has had involved parents/volunteers/and or officers, also be part or fulltime staff of school.

the ONLY way i could see an issue, is if your bylaws stipulate staff cannot hold board or committee, or volunteer positions (the latter would be absurd, in my view) in your parent group.

after all, ptos are PARENT TEACHER orgs, whats wrong with a member being both a parent AND a teacher? i dont see your concern. maybe there is more. there usually is.