The LA will always name one mainstream school, they're forced to
LAs do not have to name a MS.
They can say to LA they can’t meet needs and then the LA can’t send him there.
Unless the school is wholly independent, they can be named even if they object when consulted.
I then asked the LA who said they needed a formal response from that school and would then take that into account.
The LA must consult. That isn’t quite the same as must receive a response. Schools don’t always reply. For a non-wholly independent school, that is taken as a positive response. For wholly independent schools, a negative response.
as we wanted a SEN school we were told one mainstream had to be named, but the rest could be SEN.
Despite what some LAs say, you did not need to state any MS as a preference. Neither did you need to give more than one school as a preference.
Our local mainstream has no TAs and no possibility for 1:1. So they said under no circumstance could they take our daughter.
Obviously it isn’t now relevant if DD is in SS, but just because a school doesn’t have TAs currently doesn’t mean they can’t provide 1:1. Needing 1:1 would not be a reason not to name a parent’s preferred state MS. They can recruit.
The LA told us they can consult with s41 schools but not non-s41.
This isn’t true. LAs can consult with s41 and wholly independent schools.