Help with school please

My son was diagnosed with impulsive and inattentive ADHD around 5 years ago.  He had help and support in place in primary school, but no EHC plan in place.  He was medicated for ADHD and this does help massively.  He was then diagnosed with ASD in January 2024.  He is currently in year 9 due to start year 10 and his GCSE's in September, and he has absolutely no help in place from the school.  His one plan which I has to fight for in year 7 is still the same now.  His help is 'sit him at the front of the class', 'let him doodle in a pad' and 'use his name to bring him back to task'.  My first face to face parents evening last month was shocking.  He didn't get more than 13% in any exam and more than half of the teachers didn't even know that he had a one plan in place or that he was on the K register.  I am at my wits end with the school.  The SEND head will not speak to me and cannot give me a meeting until the 20th April.  I am looking into a peer educator to hopefully come to that meeting with me.  And I am writing to the director of education to apply for an EHC plan myself.  I need to know what help he is entitled to? and what the school should be doing as a basic?  When he was diagnosed, I was told that I would now get all of my help and support from the school and I'm just getting nothing.  Any help or advice from anyone that has been in a similar situation would be most appreciated.