Personally once someone is in school and settled I'd rather they stayed there, and it is pretty hard to get 2 children to different schools for the same start I imagine - I think it could only work if you moved both children to whatever new school they were allocated.
I can see why they did it, but in practical terms I'm not convinced it's the best plan. I don't think there is a great answer to this, but personally I prefer the status quo.