It depends on the area, Olive - my DS's school is zoned. Strictly. The school right near me is a "neighbourhood" school - if it's your closest school, you're in. If not, then you have to prove why they should take you!

I was very fortunate to live in the zone when my eldest started school, otherwise there was no chance he'd get in. Now I've moved, I don't have to move him out of the school - because he started there, they can both finish there. As I said... lucky!