Parents of children in most elementary grades in Minnesota's Independent School District 191 receive an annual notice with potentially life-altering data for their children--and they are not state test scores, attendance rates, or grades. The notice contains the child's body mass index (BMI) score, which estimates whether the student has excess body weight relative to his or her height, age and sex. The 10,200-student district is among a number of states and individual districts nationwide that are measuring children's BMI scores and notifying parents of the results, hoping such notices will serve as wake-up calls to parents about their children's weight and the health risks of obesity. Parents of students whose BMI scores are in the top 5 percentiles--95th and above--are informed by their district that their child may be overweight and at risk for complications such as high blood pressure, high cholesterol, and diabetes. In 2003, Arkansas became the first state to mandate BMI screening and parental notification. Pennsylvania and Tennessee have followed suit. However, experts say that there is not yet enough research to show that these programs work, and concerns have been expressed about the BMI measurement system's possible effects on self-esteem. Even if the approach proves to be effective, BMI screening should not be regarded as a panacea and districts need to tread carefully.