What does your child pick up from classmates?

Why is it that my kids only seem to pick up the bad habits of other children? First, let me tell you that I am well aware that my munchkins are not perfect. They have plenty of faults, but they also have some AMAZING characteristics. I'm sure that the other kids in Peanut's kindergarten class have wonderful characteristics too, but for some reason she only comes home with their bad habits. My daughter never used to roll her eyes . . . now it is an almost daily occurrence. At the beginning of the year she came home telling me about how another student in her class threw away his sandwich and just ate his snacks and dessert every day. "Can you believe it, mommy? Doesn't he know he has to eat his real food first?" was her response. When her grandparents would offer her a snack or dessert, she would politely say, "Thank you, I'll save this for after I eat my real food." I had her trained so well! This week, I've discovered that she's now throwing out her sandwich as well. Her first taste of independence and she isn't making good choices . . . What should I do?