[nikkival]

I can sympathise Willow, my son also has asthma, but at Rhyddings he hasn't had to do cross country so far so I haven't had to cross that bridge yet! Sorry Tinks, wasn't aware that they stay in the school grounds, maybe that's H&S related?
My son did have some problems last year in PE, a few kids picked on him in the changing rooms and called him a fat **** and he really lost his confidence. It got so bad that he was falling over on purpose to injure himself so that he didn't have to do PE. I spoke to the school, I dealt with the department head for PE, and completely withdrew him from PE for a few months, they were very understanding and said that they can't force a child to do something they feel uncomfortable doing and found him something else to do.
Thankfully, I've managed to boost his confidence since then and he goes to the sports centre regularly with family to play badminton and he's now back doing PE at school and hasn't had any further issues. The worst part about it is that he isn't even fat and had a complex about it for around six months.
Talk to the department head and mention the ridicule, drop the word bullying in the conversation, they don't like that word! I think you're doing the right thing keeping her off and hope that the school will take it seriously, as someone who's been there recently I completely understand what you're going through. Good Luck