OP this is nowhere near as low as schools can go I'm afraid.
Never make a phone call when an email will do - even for standard stuff like doc appointments or abscence. You need a written record of EVERYTHING. If at all possible bring along a friend who is not on the LEA payroll (Granny is preferable to parent partnership etc) so that you have an independent witness. Type of your own notes afterwards of what was said.
If a child is at P levels and a school is saying they are at level 2 say it's easy to get an independent pysch or similar (private tutoring service?) to test the child and submit the true levels. Ask for copies of the actual work that show your child is at the high standard and then get them to repeat similiar tasks under "laboratory" conditions.
I used "clicknread" a computerised phonics programme to show an independent score of my child's reading ability. Mathswhizz does similiar reporting I think. Lots of the online educational programmes let you do a "baseline" assessment to see what level your child should start at when you decide to subscribe.
Argos often do mega cheap camcorders. Use one to demonstrate lack of selfcare skills etc.
Make it obvious you will not go away, shut up or be quite under any circumstances. Drop the words "judicial review" a few times in front of any staff who might actually know what one is (the average class teacher won't).
Do remember you can name a DIFFERENT school for part 4. If a school is slack and uncooperative they won't suddenly change their spots just cos a statement appears. People either care or they don't. Don't be scared to request a different school in part 4 to the current one. If it's also mainstream tell the truth - this mob lie to much for anyone to accurately assess progress and you need your child in the care of people who take pride in their professional integrity.
If anything comes down to he said/she said Tribunal will always find in favour of the school LEA and disregard your word as a parent. They can say what they like YOU have to have the proof for everything in black and white.
You can win @ Tribunal provided you hold calm and firm in the line of total lies, character assinination and worse. It's not easy to do as they upset you so much. However do remember that's kinda their point, and the more wrong they are, the more outrageous the lies etc will get.
More Tribunals are lost cos they drove Mum to the brink of a nervous breakdown than cos the facts of the case weren't in the parents favour imho. Know this is their game and decide here and now you will not under any circumstances let them see that they are getting under your skin.
Keep ALL paperwork, never phone when you can email over the most trivial things, and stay as cool as cucumber - that's my secret formula for "how to win at Tribunal"