I totally feel your pain. I have been having issues with parents and them potty training their daughter. They're being totally lazy and expecting me to do the majority of the work.
Stupid me, I didn't have anything about potty training in my contract, but I do now!

It does feel like a thankless job a lot of the time and it seems like the parents think they can just come in and run the show. Just be sure to stick to your guns and remind them that you have certain rules and you are not swaying from any of them.