Doesn't sound horrid at all! Tracking kids seems very sensible. Not just for schools, but also for parents with kids that run away all the time (so almost all 
), e.g. in shopping malls, amusements parks, etc.
For Trackey, we plan to into dive this use case after the pet tracker. Main difference we could think of between pets and children is that you also need to track them inside buildings. Also, you can't make them wear collars 
@GaryMortimer, I'm curious to know how the GSM trackers are attached to the kids? As wearables? Any limitations there? What kind of disability school is it? Do you only want to track around the school or in a wider neighboorhood?