Anyone having a hypo is a scary thing. Having been married to a type 1 diabetic whilst I was teaching did actually come in handy, as I could recognise a hypo and correct if necessary. I always had glucose tablets in my bag. Other teachers knew. If there was a diabetic, he or she would often have a bottle of Lucozade to hand to the teacher.
Even as far back as the 50s there were diabetics in normal schools. They survived. The difference now is, as GT says, the number of injections. It's to do with keeping tighter control of diabetes. It always used to be that the diabetic had to have an injection 20 minutes before a meal. With the different types of insulin now, it is possible to have an injection with the meal or even after the meal, so the timing is not so strict.
It's not just a problem in schools. It's also a problem in nursing homes. I know of homes where there is only one member of staff who can give injections. If that member is not there, a district nurse has to be called in. That must be wrong. There should be a trained member of staff on duty at all times, considering the increase in diabetes in older people.