dev, it's because it is a much bigger deal for you than it is for them. It is your life. Their lives are about meeting a class of 30, about preparing their lessons, about logistics of their own childcare arrangements, and about probably dealing with anxious parents who are contacting them.
You're taking it too personally. I agree it doesn't sound like a particularly caring school towards your ds, but I doubt very much my ds' school would do it either. We, SN parents are often set up from the start. As a parent of a child with a SN you are, by definition, troublesome, but how can we not be in the current system?
What parent is going to know how badly her child is being failed and not make a fuss of sorts.
But this time you have the home tutor, whom he knows, to support him. Keep an open mind. It is a new year, a new teacher, and a new arrangement. Try to be as positive as you can and as hard as it is, do try and be determined to make it work, so you know if it doesn't you really did do everything, and if it does, - well excellent.