I went to High School with a girl who had a disorder and while she was clean, it created an odors, might seem like BO but was a medical problem. I can still smell it if I think hard enough (smell memories are strong).
High school kids being HS kids and fact she was heavy and not very cute, sure HS years were a torture for her.
Everyone knew she had a disorder but weren't very nice. Not direct teasing but totally ignoring her.