Help with discrimination in Secondary school.

Hi, this is my first post here and I'm hoping to get some help as we are getting increasingly desperate with our sons secondary school. My son is 13 and had a diagnosis of ASC in 2016. 

Since he started at Secondary school we have had probllem after problem with the lack of help, or allowances made for our sons difficulties, he doesn't have an ECHP and I have never

seen his MyPlay (Which every SEN child in the county must have). He is being sent to isolation (12hrs at a time) on a weekly basis, in line with the behaviour policy. Things have come to a 

head today, when he was accused of smoking. He had had a cigarette flicked towards him (not deliberately, he was crouching behind a bin playing with his phone!), so he picked it off his

leg, stood up and ground it out with his foot. A teacher has witnessed this, but not the throwing, and has taken him to the Deputy Headteacher, where he "wrote a statement". Despite him

explaining his version of events, the teacher told him that he "Reeked of cigarettes" and sent him to isolation. Whilst in isolation he began to get angry and approaching meltdown and said "I

want to die". He explained to me that he was "just messing around" and the Head of KS3 has told him "Maybe you should look at other schools then, seeing as we cant help you."

Now, I always take things he says with a pinch of salt, until I have spoken to the school, but in this instance my husband received a phone call from the Home school Liaison voicing concern

about our sons demeanour and well being and she clarified that they had asked my son if "If he was happy, or wanted to go to a new school.". We are so angry about this and feel they are

attempting to push him out or force our hand to remove him and would really appreciate some advice on what we can do. 

Apologies for the length of this post and welcome any advice given.