I think the point is that, like a lot of cost problems, a relatively small proportion of users end up accounting for a relatively large share of costs. Just excluding those expensive users (implicitly or explicitly) is a ‘neat’ way to reduce costs and improve outcomes at a particular school. Unfortunately under a funding-follows-kids system that leaves a small population with $X in funding that costs $10X to serve. Maybe grouping all of those users provides enough economy of scale, but that’s not obvious, and sounds a bit like an asylum to boot.