A few things here in terms of things you can do:
1. You need to find out exactly what is happening with your son on a day by day basis.
When is he part of lessons? What do his adjustments look like? Why is he given additional time outside etc. There may be perfectly valid reasons: having support in place does not mean that his education will look like everyone elses'. Usually, there will be differences to take account of needs.
2. Identify another specific school (ideally one with an RP)
If, after everything above, you don't think the school are supporting him, you need to look at other schools with better SEN provision, such as those with an RP unit attached. You need to know where you want him to be rather than asking the LA for a general move.
3. Request an early review of his EHCP.
Use this to demonstrate that the school is not (and can not) meet his needs as outlined in the EHCP and request that the named school be changed to the one you identified earlier.
However, you also need to know a few things, moving forward so that you can effectively judge the provision in place for your child:
- the local authority will always say that the mainstream school can meet a child's needs until they are forced to change their stance. This is because it's cheaper for them.
- when the school says that your son's needs are some of the most severe that they have dealt with, this isn't to upset you. It's simply a statement of fact so that you understand more about how your son can or can't function as part of mainstream education.
- off-rolling is the act of kicking your son out of school in order to get him off their register. Being outside the classroom is not off-rolling.
- education for autistic children (or any child with additional needs) may look different. That doesn't mean inclusion isn't happening as long as his needs are being met.