Good thread!
The school I teach at was a sink school years ago. Now we're over subscribed and down to word of mouth NOT OFSTED as we only got our first 'Good' grade (we're a relatively new school) last year.
Parents who are actually in our catchment area still hold the misguided belief that school M is a better school than school B and when they applied they put only school M down with the very misguided belief that because they only put one school down, they would get that school.
When the allocations were made, there were obviously other families who put school M down as their first choice who were either in the catchment area, had siblings or were closer. They ddin't get their choice - 16 families were now given school G which is now the 'sink school' because they had places and nobody wanted to go there! They tried to get into their catchment school (school B) but they were now full from just the first choice families and some of those lived OUT of the catchment area. They weren't given school B (the 16 families) because they led the council up the wrong path in the belief that they weren't actually bothered which school they got.
Now my child is starting school in September. He does go to the nursery and I do know that I still have to apply for a placement I know I will get in (school is rural, recently good from a fall of Outstanding to Serious Weaknesses) and only have avout 2/3 of the places available. BUT ... I still put down three choices as a 'just in case'.
All families are given guidance and the rules and regulations of applying by their councils and all councils tell you to ensure you make three choices.
You would be stupid not to. However I know that in larger more urban areas such as London, you still may not get your preferred three choices.