"from a Tribunal perspective the question is always raised - if things are that bad, why didn't school apply?"
But surely that is because the Code specifically mentions that a SA request by a parent may be a reflection of dissatisfaction in the School's actions?
"7:21 Parents may ask the LEA to conduct a statutory assessment under section 328 or 329
of the Education Act 1996. The LEA must comply with such a request unless they have
made a statutory assessment within six months of the date of the request or unless they
conclude, upon examining all the evidence provided to them, that a statutory assessment
is not necessary.
7:22 When schools, external specialists, including LEA support and educational psychology
services, and parents have been working in partnership at School Action Plus, the
parental request for a statutory assessment will usually have been discussed between
them. Therefore the request is likely to be an approach agreed by all the parties involved.
The parents may then, with the help of the school, be able to provide the LEA with the
evidence listed at paragraph 7:13 above. Sometimes, however, a parental request for a
statutory assessment may be a reflection of dissatisfaction with the action taken by the
school. Whatever the reason, the LEA should take all parental requests seriously and take
appropriate action."
I agree that Tribunal will ask. I disagree with the reason your chap gave.
Given the timescale, it won't do any harm for the school to spend time preparing while you write a letter now. The only difference is that if you wait for the school, you have NO chance of the school getting the evidence request before the end of term, which means that the timescale is lengthened.
If you do the request, you gain 2 weeks on the timescale, and the school are preparing the evidence anyway. Win Win.