Whose address do they use for catchment area if you share custody 50/50?

[MrsHicks]

My husband and I are separated and my little boy spends alternate nights. He'll be starting school next year and today I was wondering how they'll determine catchment area. My ex lives about 400 yards away. I am closer to the 2 schools we'd like my son to go to, he's closer to another good school that would be our 3rd choice. Do we just nominate one address and say that's his main address? Of course, our arrangement may change later down the line but it's working really well at the moment.

The normal answer is that it is the parent's address that the child spends the majority of the school week with but in your case that will not apply if you share custody 50/50.
You need to speak to the LA admission office and get a definitive statement of what they will do and get it in writing, so that when you apply their can be no issue over mistakes over the address.

Who has the child benefit award?

I think it is the address that Child Benefit goes to.

Thanks for the replies! The child benefit comes to me, but I'll speak to the LA admission office too and find out.

The only case I have experience of the father had the child Monday Wednesday and Friday ( plus alternate weekends) so his address was considered for secondary admission.

Admission is right - it is up to each LA to decide its own policy on this. There is no national rule.