Tribunal order- School now saying not appropriate provision for him citing - school structure, student cohorts, and his specific needs

Child is 13yrs old, attending special needs maintained school (yr9) diagnosis of severe learning disability.
I went to Tribunal earlier this year (April 2024) re appealing Sections B & F of the EHCP. LA professionals incl SLT, OT and Educational Physiologist reports were complied as part of the reassessment of his needs.
The EP report I felt was a fair representation of my son's needs, in particular (as example) citing his sensory needs related to the classroom environment, low arousal, to be in a classroom environment with peers with low sensory needs i.e ''no stimming'' as an example.
The LA SLT report recommended he needed 1:1 TA hours for core subjects, 15 hours, weekly for core subjects- English, Maths, Science, PSHE.

The Tribunal hearing was held in April 2024, with the Final EHCP issued by the LA in July 2024 (no amended Final draft EHCP issued, only Final).
An 'implementation' meeting was held with the school at the end of September, with a detailed plan given to me by the school of how they had started to implement the 1:1 hours TA hours weekly and an updated timetable was given to me. At the end of the meeting I checked whether the school had received the Final EHCP to which they responded they hadn't- they had only been working off the Tribunal order. At this meeting, there was no indication from the school that they wouldn't be able to meet my son's needs and the Tribunal order, it was a positive meeting.

On 14.10.24, I received an email from the school saying that after reviewing the Final EHCP, and discussions with the senior leadership team they felt that the

' School was not the most appropriate provision for Xxx. Given the structure of the School, and the nature of our student cohorts, many of the elements within our school are not compatible with the specific needs that have been identified in the updated EHCP''

School said they would be arranging an Emergency Annual Review meeting, I have yet to receive the date of this meeting.

My son is very happy and settled at school and a possible change in placement will have significant negative impact on him and us as a family (his Dad and I are separated).

Where do I stand legally and how do I best prepare for this meeting please, and also preparing for the worse case scenario? I am very worried.