There should be something in your by-laws that goes over this. The funds have to be allocated to another non-proft org,. Technically you can give the funds back to the school system. Once the account is empty you can close the account, just make sure your completely balanced before you do so!
I know this sounds crazy, but my school is closing and I have to cancel our PTo account. I'm the PTO coordinater for my group. How do I cancel our account. I don't want all the information hanging around for people to get to.