Suspensions

Son is 6 years old - suspected ADHA,PDA and Trauma related anxiety (owing to my incurable cancer diagnosis). He is in year 1 of a primary school who were very slow to acknowledge his SEN needs, despite paperwork backing this from age 3. He has a sen support plan in place, along with a positive behaviour plan - both heavily written by me as the SENCO is very inexperienced. He now has 1:1 at all times he is in school - with a note in the sen plans that he should be with a trusted adult at all times, because of a flight risk and risk to others. This year he has been suspended 3 times already with the last suspension being 2.5 days for spitting. The situation occurred because his trusted adult was not with him, no adult was. My question is - can the school really suspend him, when they are failing to stick to what's been agreed and counter to the plan, fail to identify new triggers and learn from experience. Many thanks legal brains for giving your time.