Pa State law says it is unlawful to possess any firearm on school property but "It shall be a defense that the weapon is possessed and used in conjunction with a lawful supervised school activity or course or is possessed for other lawful purpose".
I have always been told that even a CCL holder cannot carry on school property. What is your interpretation or opinion of what is in bold text.
Here is what the Brady Bunch has to say about this.
State law does not clearly prohibit people from carrying hidden handguns into schools if they have an easily-obtained CCW permit. The law provides a defense for CCW permit holders to carry a gun into school "for lawful purpose."