School warnings about children's weight don't work, study says

(CNN)The letter or report card is from your child's school, but this grade doesn't have anything to do with school performance or behavior. Instead, it's a measure of your child's body mass index or BMI -- designed to warn you when your child is overweight or obese.

It's a well-intentioned public health program, recommended by the National Academies of Sciences, and created to combat the growing