You can find the PIAA physical form HERE. You must have a completed physical to participate in any PIAA sport. The physical must be dated after June 1st of the current school year. (Ex- For the 2013/14 school year, a physical must be completed after 6/1/13).
You must also have a completed Permission to Treat form. You can find that HERE.
For the winter and spring seasons- if you already have a completed PIAA physical you will need to submit Section 7. You can find that HERE.