Wow Claire, this is such a heart-breaking story. I can't believe this was ever allowed to happen. I'm so sorry you went through this.
Also, I definitely agree with your point about BMI and being an athlete or even just having muscles. I think BMI is a really stupid way of measuring anything. I have fluctuated between size 4-8 all my life - but according to my BMI I am obese.
What an absurd thing to measure and especially for young kids.