School help- teen escaping

Hi everyone 

im hoping someone can over advice at very short notice.

My son is yr 11 has autism and adhd. In 2022 he jumped the school gates for the first time due to the school not listening to him or me about the struggles he was having with a couple of students, he was also struggling to deal with the lose of his Grandad. He reached the point of fight or flight- knowing he would be in trouble if he let lose on them he escaped. The school put him on a “safety plan”. Meaning that if he didn’t arrive to lessons slt were called and school searched, he walks out of lesson the same, if he escapes school myself and police called.

well just before Easter we had a very similar situation in which a pupil was saying disgusting things/ rumours and basically bullying. My son hit him once but the boy continued- I was made aware after the fact. I informed the school their response was they would put them in a room together to talk. I advised against it by phone and email but was ignored. They attempted it anyway. This led to my son escaping again. But it was during lunchtime. He text me and I collected him from the local high street. I expected a call from school 10 minutes into the lesson after lunch- it didn’t come. 10 minutes before the end of the school day I called to see if they knew where my son was ( I know, I was playing games and had actually dropped him home and gone to sit at school as if I was there to collect him as normal). They had no idea and would call me back. Again no call. 5 minutes after school finished deputy head walked past the car and I asked him what was happening- as dsl he had no idea so went back into school to find out. 30 minutes later he came back out saying he had seen on cctv my son had escaped at 130- it was now 330. My son had been “missing” for 2 hours.

i have sent numerous emails to school, local authority departments regarding this and now have a meeting tomorrow with the head teacher. The school are saying its human error and they can keep him safe/ at school. But it’s the second time!! They are refusing to have a member of staff with him as much as possible and have offered to call every lesson to let me know he is there. 
I know this won’t happen. I also have the issue of my son not wanting to be there and threatening to keep doing it. What can I do? What can I request as adjustments? 
thanks for reading it’s very long