Essentially, the system is 'blind' and the algorithm is programmed with the assumption that parents have read and understood the guidance provided and acted accordingly. So if someone puts Catchment School A first, not because that's the school they most want their DC to go to (which is how their LEA guidance will tell them to do it), but because some scaremongering ignoramus at the school gate has told them that if they put Selective School B (that they really do wamt) first and don't get in, they won't get their catchment school either, 'because it will fill up with people putting it first', if they can be offered a place at School A, that is what they will get. The system doesn't go,
Oh look, they put School A first, but qualified for School B and no-one wouldn't really want School B, so I'll allocate them School B. Seriously

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