How can I push the school harder?

My son has CP. He finds working with numbers very hard. At the moment he is at level three in maths. His chronological age is 15 years and 4 months. He has recently learned to tell the time but hasn't any concept how long 15 minutes is.Hes easily lost and clings to me outside when we are going somewhere new. He's not had a psychologist report since he was nine years old. Our school said because he advancing in English he doesn't need one. He's at level four for English. But his reareading score of understanding is lower four. His maths teacher left our school and now the school have doubled the class size and they have one TA. He will receive a U in exams for maths. He. Forgets how to do the eqequation in basic maths. They are being urged by the government to stick to a timetable which left him long ago but still the teacher expect him not to catch up but take something away. I am told he will be doing in class grading but this doesn't allow him any posable forward achievement. He's very good with computers and wishes to be able to go to college to study them but without any maths qualifications he's not going to be able to study computers in collage. This is his final year of school before his transition to college. The school are not concerned about him getting a maths. I don't feel right and accepting their decision feels though I haven't pushed enough for a better outcome. Can advise me on how I can push the school harder or should I accept thatright hhemiplegia might be responsible and not the school. ???