Middle School Girl Pens Heartfelt Letter Explaining Why She Won't Measure Her BMI for School

— -- An eighth-grade girl's letter promoting a positive body image and explaining her refusal to calculate her BMI for a school assignment has gone viral, drawing attention to problems in using an outdated measurement system for student's bodies in school.

In the letter, precocious Tessa Embry writes, "Ever since I can remember, I've been a 'bigger girl,' and I'm completely fine with that; I'm strong and powerful...."

"But, at the beginning of the year, I started having very bad thoughts when my body was brought into a conversation. I would wear four bras to try and cover up my back fat, and I would try to wrap ace bandages around my stomach so I would look skinnier....My doctor and I talked about my diet and how active I am. He did a couple tests and told me I was fine....My BMI is none of your concern because my body and BMI are perfect and beautiful just the way they are."

Finally, the middle-schooler writes,

"In conclusion, BMI is an outdated way of determining a person's body health, and it's a measurement that SHOULD NOT be used in a school setting where students are already self-conscious and lacking confidence in their unique bodies."

The 8th-grader makes a valid point, according to Keith-Thomas Ayoob, a nutrition specialist and an associate clinical professor in the Department of Pediatrics at the Albert Einstein College of Medicine in New York City.

"I'm not a huge fan of measuring BMIs in school. Too much opportunity for stigma and inappropriate conversations and there are better things schools can be doing to promote healthy weights," Ayoob told ABC News today. "She's correct but more information is necessary."

What we measure as BMI today was actually a formula developed in 1832 by Adolphe Quetelet, in his quest to define the "average man," according to the U.S. National Library of Medicine, which is part of the National Institutes of Health.

The formula to calculate BMI is your weight (in kilograms) over your height squared (in meters).

"BMI is a measure of weight based on your height. It doesn't tell you about body composition," Ayoob noted.

Mindy Embry, Tessa's Mom, told ABC News today that her daughter plays softball year round, and her primary position is catcher.

"She has always been one to question the norm." Embry said of her daughter. "If she saw something she didn't think was right, she wanted to make it right."

"We're really proud of her for standing up for what she believes in," Embry said of her daughter. "She has got a special gift. She's strong. She's powerful. She has a healthy diet and she is active."