The same EXACT thing happened with Pandy. Before we moved to where we are now she loved kids, let them pet her etc etc. Then we moved here and for some reason she started barking,snipping, hair raised on her back at the kids next door. I couldn't figure it out - then one day I saw one of them poking her w/ a stick through the fence and I knew that was what had happened. I immediatly took her and had her evaluated by a dog behaviorist and he told me that once they get teased etc by the kids that's what sticks in their mind and the odds of that changing are slim! So now we have to keep her away from kids - she actually bit one last year in the face - only a minor nip - but she was trying to bite him hard. Sad. I hate it - but I would keep him indoors and when kids are around make sure you tell them NOT to tease the dog - my neighbor kids still do it and I constantly tell them not to.