I've had this happen numerous times and still do. I think a lot of children get away with a lot more with Mom and Dad than they do than they do with us. Once Mom and Dad walk in, they know they are tired and probably won't fight them on much, esp since they haven't seen them all day. Not many parents want to discipline their child the second they see them for the first time in 8-10 hours. I also find it true for really young kids because they are just having so much fun playing with their friends that they don't want to leave. It bothers me as well to know how well behaved a child can be all day but then once Mom or Dad walk in the door, this little monster comes out!!