You may be thinking "PTO"?  I thought it was "PTA"? 
Here is the difference between the two:

PTA is a national organization that requires members to pay dues to both the organization and the state and abide by state and national group rules. PTA groups also have a political voice, as the PTA maintains a Washington, DC lobbying office. So, only dues-paying members can call themselves "PTA."

PTO is a more generic term. It generally represents the thousands of groups that choose to remain independent of the PTA. PTOs are most often single-school groups that operate under their own bylaws and concern themselves with the goings-on at their building or in their town only.

For more information on PTO's, check out the PTO Today website