sorry about multiple posts, but honestly on school applications threads I get so irritated with people who know bugger all about the process posting crap.
School admissions is a legally controlled process. So if I think that the council has not acted fairly, they are legally obliged to correct it, hence the kids in reception who get kicked out of school, when it has been shown the places were given incorrectly.
Their procedures do vary, one council takes child benefit, one takes electoral roll etc etc.
They do have differences if you are moving, one will accept the solictor's email confirming exchange, other insist on waiting until completion and paper evidence.
But each council must have, by law, a written application process which takes all this into account, and they follow it. And it you try and cheat it, and get caught (and yes, obviously some people don't get caught) you will lose your school place, and then you will have NO PLACE and have to apply again, and are left with the dregs of places in all the schools that no-one wants.
It is not worth it. And it is your chidl who will suffer.