We have had similar responses to written confirmation of what was said in meetings Limbo. Including the meeting when the SENCO said that not only would they refuse to be named if we persisted with specifying and quantifying his statement, but that absolutely no mainstream school would take him.
It was one of the few occasions when we actually received a written response to our letter and the climbdown and backpedalling was a wonder to behold. 
I still think it was worth doing though, as what the school didn't know was that between that meeting and writing the letter, we had spoken to both the LEA and IPSEA and related the whole story to both. Both of them then told us the school is not allowed to say what they did and to request it in writing.
Sounds like your school uses very similar tactics to ours, since we got our new SENCO.
I had the same dilemma re siblings, plus the school is across the road from our house and I am unable to drive, so moving them would not only cause a lot of upset, it would also be a logistical nightmare, not to mention all the other local schools are oversubscribed and no better - and in some cases worse - re SEN.
I have ds2 in year 4 and dd in the nursery there, plus despite everything he's been through, ds1 loves the place. Most importantly though, ds1 had finally started to make friends and integrate a little socially when we were going through the statementing process. To be honest, I valued that along with his happiness more highly than the academic side of things.
I can't wait until ds1 leaves in July, but have had to retain at least civil relations with the school, as I have another 7 years after this one of dd being there to get through before I can finally be free of them.
I was reluctant to involve PP as well as, being funded by the LA, they always felt like 'the other side', iyswim. In fact we didn't involve them until the school wasn't implementing the statement provision at all and dh had started a new job, so could no longer attend meetings with me. I was pleasantly surprised. I can't say they helped a massive amount, they very much towed the party line and tried not to rock the boat too much, but the rep that came with me 'read' the situation straight away and had seen it hundreds of times before and it did feel like she was on our side - but restricted by red tape and 'rules'.
She did confront the SENCO on a couple of important points, most notably on ds's rights to have access arrangement for SATs, as she sat there and listened to the SENCO bare-faced lying to us - again - that he would have to be tested and she would decide whether or not he would get access arrangements.
The PP lady knew her SEN law inside out and immediately confronted the SENCO, told her she was wrong and that due to his statement and test results he was automatically entitled. She also made it clear that the strategy the school was using on not allowing him computer access in class, so that ultimately it wouldn't be considered typical support for him and he wouldn't get it for SATs, was not legal and they had to allow him the access his statement specified.
She was also the first person to tell me I was wasting my time and energy trying to get this school to take their responsibility and legal duty towards ds seriously, as they were obviously never going to change and I would be better placed putting my energies into getting him the best possible placement for secondary. I was appalled at the time and totally disagreed. We carried on fighting for another couple of months, to no avail, until we realised we were just banging our heads against a brick wall, she was right and we just have to cut our losses and carry him through the end of this year. Then we went all out to get him into an extremely good out of area independent mainstream with a specialist interest in ASD and I'm so glad we did, because the place is perfect for him and he now has it named on his statement.
I don't envy you your position. It is a horrible situation to be in and very isolating. Do keep posting, even if it's just to remind yourself that you aren't alone with it all.
