Refer the school to your GP and tell them to take a long walk off a short pier! Would they rather she was at school and suffering, having to be sent home etc etc?! The poor kid can't help it FFS, schools can really be a PITA at times
Have you seen a nutritionist to discuss diet and what foods to possibly avoid? I know certain foods trigger head migraines so I'd guess the same foods probably trigger abdominal ones. They say chocolate os a trigger, but if I have a migraine, that's about the only thing that I can eat without feeling like crap!!