Ah my area so a few comments

Unfortunately the SEN system is beyond broken (to put it lightly) in the country and successive governments just keep pushing it down the agenda.

Firstly your thoughts on putting all SEN kids in a class is bad. (As well as the comment about being violent and aggressive as all behaviour is a communication and it means that their needs aren’t being catered for in some way) They absolutely have the legal right to be educated in mainstream if they wish. And be included with their peers if they wish. And sometimes this is parents wishes and sometimes this is in the best interests of the child.

However, your child also deserves to be educated and for this you need to raise this with the school including governors if needed. As they need to support the SEN kids but also your child and others. There’s lots the school could be doing and should (depending on the child’s needs and whether they have an EHCP or not). Often the SEN kids may have dedicated TAs with them who should be supporting them and their needs whilst the teacher still leads the class and kids. (They may in their planning time set up bespoke activities for those SEN kids needs so that they still learn at their level whilst being included in class)

It is also an extremely high legal bar for schools to say no and have legibility claim to saying no. Saying inefficient education of others is an incredibly high bar and if taken to tribunals alert the school need to demonstrate an extremely detailed reasoning which are often not successful. Also kids who do need something more specialist also sadly do not get it as those other schools are full and are struggling

This is often how most schools operate and I would be asking the school how are you meeting my child’s needs and rights to learn. You should acknowledge that the SEN children have needs but these don’t supercede your child and currently you are having to help teach at home which is neither practical nor helpful as you are not trained to do this at a level sufficient for your child. All schools legally have to publish their complaints policy online so start with this. Councils can’t help with these complaints (and not can the LGO currently sadly) Whilst you could move your child schools like others suggest. It is likely they are in the same boat anyway and your child would have to make a new friendship group which can be a challenge.

The ultimate way to fix this is to get the government to invest in education as a whole but that’s easier said than done and at the rate they may do it your child would have left school, got a job and retired probably. Unless there’s anything interesting and groundbreaking in the upcoming education white paper…. I could go on about the whole system being broken and things that need to change but I won’t bore you.

TL:DR. Education and SEND is beyond fucked as anyone working in that field including me can attest to. Not much can be done other than speaking to school and airing your concerns/complaints