My children's school goes a lot farther than the "No peanut butter" rule
Their school rules are:
No peanut butter or nuts
no prepackaged granola bars or breakfast bars
no "lunch-ables" lunches
no fruit roll ups
basically no dessert of any kind
At first I thought it would be hard but now I like it... they just don't get any junk food at school, I don't have to worry about them eating a bunch of M&Ms at recess and coming home all hyper...But they even have a guideline that foods like yogurt and such should be put in reusable containers because they try and have a trash free lunch time.