Why? And which children are you going to apply this to?
Lots of schools also start GCSEs in Y9 - DD's has a 3 year pathway.
Once the council has offered a place and it's been accepted then it is locked in until end of Y11.
Can you imagine the court cases if councils started moving children around from school to school, and the disruption to children's lives and friendships.
Child A moves house and no local place, so council send him 15 miles away and pay for transport. 3 years later local place is available so council decide he must instantly move schools causing potential emotional and educational detriment... the lawyers would have a field day with that!