Even if that's what's happening, what would you say as a parent if you had applied for secondary school for your child, presumably carefully examined the local options and decided on school A. You were delighted to get a place at school A, bought a uniform for school A and sent your child off to school A, only for them to be bussed off several miles to school Z where they were expected to spend the rest of their school career? While technically remaining on the roll of school A? Doesn't that make a bit of a mockery of the admissions process? Even with managed moves where a child is doing really badly at their chosen school and are at risk of expulsion, the parent has to agree to the managed move.
I was thinking a bit more about the idea of transporting SEN kids around as we do at sixth form for different A-level choices, and I was thinking about the children in my school that this would affect. The children with SEN who would qualify are the weakest and often most vulnerable students. They are often in the most need of stability, routine and a familiar environment. The idea of shuttling these kids back and forth between different schools, however great the facilities at the other school, just wouldn't be fair on them. Besides, any time spent on a bus, they definitely aren't learning. Our sixth form timetable is managed so that the buses don't affect lessons, but a sixth former has free periods and so on so sitting on a bus during lunch isn't too much of an issue.