You are very smart, that is a fascinating question
Regulations on legal drugs exist to keep them away from teens and children. Hope this helps and good luck on the rest of your homework!
I do not think that they should send notes home because BMI is not accurate for many teens and children. The BMI is not accurate for people involved in sports or people who worked out. This would not be affective, there are more effective if they found out their ways to detect childhood obesity. For these reasons I do not think that agencies would support using BMI but maybe something else