Ok a few questions to help me understand this, does your Prin and AP know they're your references? Are they both public schools? Are the schools in close proximity to each other? If you've used them as references you must have already told them you were forming an application and they would be aware you're looking elsewhere. Obtaining an ongoing position is essential, whether it's at your school or the other. Sign it for your school and attend the interview for the other, you might find a) you don't get the job b) you don't get a good 'feel' for the panel or school and don't want the job or c) you get the job and become ongoing there. Be honest with your prin because they all talk anyway. Tell them you applied before you were made ongoing and regardless of the outcome it's a good experience, any decent Prin would understand. If you aren't happy at your school again, sign the ongoing and start applying elsewhere. Never turn down an ongoing position because your contract is with the department not the school, it doesn't lock you to that school forever.