Every public school has a local PTA and they are officically independent, but all members are connected to the National PTA. (www.pta.org). This is where parents and teachers get together and decide the course of their children's lives from kindergarten to eighth grade. They are the people who discuss which books to ban, decide what you can wear to school, and have bake sales.
In highschool it all changes (at least locally). The entire organization makes the bold move of adding the letter "S". The PTSA still answers to the PTA, the membership cards still say PTA, but the local newsletter has the letter "S". Most of the rumors tell us that the mysterious letter stands for Students. Silly rumors.