Well GPS works by sending a signal into space that gets a satellite to pin you on earth. So if you trying to turn off the ringer wile in school you would have to make a app that gets the satellite to pin you on the map then say if your in school or in like a 5 mile radius of your school to tell the app to turn off your ringer on your phone.
Your app would need;
Your Schools location, Your location, Your ringer state(On/Off), And it would need if you have school they day(Like on the weekend).
Then you just have to put it together