Ignoring a child's growing waistline can also be tantamount to child abuse, according to Emily Abbott, who teaches high school in Tacoma, Wash.
"Though I am not a mother, I would expect someone to step in and help if I was doing an ill job raising my child," she said. "Accepting and allowing obesity in children is slowing killing them and setting them up for an early grave."
New York nutritionist Keith Ayoob agrees that collecting BMI data is a "starting point" for addressing the obesity epidemic.
"You want to find out what the contributing factors are -- 9 times out of 10, it's not in school but the other 18 hours of the day," said Ayoob, director of the Nutrition Clinic at the Rose F. Kennedy Center at Albert Einstein College of Medicine. "We worry about what's going on at home."
Often parents seeking help walk into his Bronx office for a half-hour visit with a shopping bag full of chips and soda. Others say they have never offered their child fruits or vegetables.
"We owe kids better than that," said Ayoob, "Parents need to learn to be parents and set healthy limits and let you know they are in charge and this is not a democracy."
"When parents give kids food, they are training them, not just feeding them," he said. "Parents sometimes have to deal with their own eating issues."
Such was the case with his patient, Karen Butler-Brock, whose son Andrew is overweight and has a family history of diabetes and heart disease.
"He had insatiable appetite and the pounds were packing on," she said. "This kid is genetically coded for disaster and has to remain a healthy weight."
By the age of 7, she started to notice Andrew's weight gain. "He's a kitchen raider and a food hoarder," said Butler-Brock, who works for New York City's United Federation of Teachers.
But with the help of Ayoob, she made dietary changes: introducing green vegetables, measuring starches, eliminating snack foods and changing from whole to skim milk.
Today, at 13, Andrew is "still fighting the battle," but has made improvement, according to his mother.
Now, she is an advocate for BMI surveillance, hoping it will also help low-income communities like the Bronx, where childhood obesity is rampant, to generate more health programs.
Ayoob agrees that BMI testing ultimately belongs in the hands of professionals and not gym teachers.
"Doctors are the gatekeepers," he said. "And parents trust doctors."