I think the first step is to read the reports and see if you see your DS in them. Have they understood him? (If no, then contact the report writer/ LEA)
If yes, then photocopy them, get a highlighter & highlight every statement of need. Check if it is represented in Part 2. (If no, list what is missing)
Then, look at Part 3,and see if there is an action point for each need. If yes, is it specific, quantified and measurable? (If no, list what is missing)
Then, make sure that anything like OT & SALT needs are in parts 2&3, not part 6.
Then, look at the level of support (1:1, small group, therapy) and see if it is sufficient (if no, write it down).
Then look at part 4 - it will either say mainstream, or indicate special with some sort of phrasing like "a setting with an enhanced pupil/staff ratio with staff skilled and experienced in teaching children with learning difficulties" They are not allowed to say "special school", I think, as you have a right to mainstream education in 99.9% of cases. It may also give an either/or phrase.