One of my friends recently told me that she's teaching her 4 year old about who can and can't tell him what to do. That seems like a good age to get that stuff sorted out. Unfortunatly for kids that get passed around a lot when they're 4, they are not as easily able to get it all figured out then.
So we have problems like, "My teacher said that I can bring toys to school to play with while I'm on the bus, and my bus driver said it's okay - so they win". But see, when the parents say no toys at school, it doesn't matter what teacher and bus driver say, the answer is no. Parents win.
Why is this so hard to understand? Probably for the same reason it's hard to understand that just because "my brother said it's okay" doesn't make it okay if it's against the rules.