I would also request that they please do their best at home to follow through as well. although it is fairly natural for a child to explore (out of 50+ kids over the years I have had a few) it is still a bad habit to develope and really not something they need to nurture at home, he should be corrected when caught doing this at home or in your home....as you are doing, and if they can't work with you or help support your concerns with a onsie, then termination should be considered. What will you do when he begins potty training in a few months? perhaps that is his issue? maybe he can feel the "need" to pee and it makes a little tickle? perhaps he needs to go to the potty when caught with hands down pants? he is at the age I would be training, if not earlier.