How about getting permission from the principal to let you practice flying at the school. That lets you practice your recreational flying on the property. If you operate the aircraft within the rules of hobby, stay below 400 feet, don't operate over assemblies of people and don't overfly private property, you haven't violated any rules. Have fun and go home. If you get a good shot while you are practicing, save it. If they see it somewhere and like it, you can let them have it. You didn't contract to take photos for them, you took the shots for your personal satisfaction. Your son plays sports there and you were taking personal mementos using a new technology. BTW, who's making waves for you? Are they likely to "report" you for your activities, or are they just offering their HO? Consider the threat and assess the risk. JMHO...