I'm having a card printed for a friend and I want to print inside Love from all at St. Peter's (shortened for St. Peter's Infant and Junior C of E (Aided) School). I do not want to print the full school title as it is too formal but I want to get it correct, as all the teaching staff would have something to say if I slipped up with the apostrophe! I know you do use an apostrophe for possession and the school belongs to St. Peter in a way but if you don't want to write the full title, is it... St. Peter's or St. Peters? (but it is not a plural either... confused!) Anyone like to help me out?
You probably refer to the school as St. Peter's frequently without all the following words anyway, so this occasion is no different, assuming that the full title is possessive as you've written. It'd be no different than if the school were named The Tudbury Institute of Fine Arts, Mechanical Engineering, and Home Repair: You'd certainly just say, "I'm going over to Tudbury for a while."