I found that for some of my DCK's the more I push the less they do. So I show them what they need to do once in a while ... when one of the other kids do it I praise them and OUPS ...Suddenly the other child will start saying thank you or please or do whatever I want them to learn to do. But you I would mention it to the parents what you are now trying to teach their child. I have before. I bring it up just like that in a conversation about their child and most of the time, the parent clue in. Good luck !