Not sure if it is my hormones, but I can't find the relevant doecument on line - so I am going from memeory of what we did last year. Things can change slightly from year to year but not lots and lots. BTW - am a Year six teacher and head of year six - but that doesn't make what I am going to say totally correct.....this is what has been the rules for about 6 years though.
Applying for extra time
Schools have to fill in a form from the 'Special Arrangements' booklet that the QCA (the examiners if you like) have sent the school. They need to fill out the form and be able to demonstrate why a particular child needs extra time. So they often have a statement or are high up on the SEN register. They need documentation of this - the school should have copies of your DS's IEP stating that completing work in a given time is a 'target' for example. From what you say, I am sure that the school can justify him having the extra time - they need to fill in the form and send it to the relevant person at the LEA. They will have gone through this procedure before. You need to ask them if they are applying for extra time, and if not, then why not. DS should be entitled to it IMO.
With this one though, there is a deadline, and I believe it will be some time soon so that is something that I would chase up. Don't let school fob you off and say it is just for children with statements. Rubbish - though it is harder to get extra time for unstatemented children.
Scribes
Scribes are used for children who are 'physically not able' to write legibly at the speed required for the test. There doesn't need to be a physical problem but it is clear from what you have said that your DS will struggle to be understood if he writes for himself. Schools do NOT have to apply to do this. There is a special form in the booklet I mentioned above which the teacher has to fill in for each test and attach to DS's test explaining why he needed a scribe. But scribing must be 'normal classroom practice' for the school to be allowed to do it. So if he isn't scribed for at school on a regular basis, he isn't allowed to have it for the tests. Perhaps a chat with school to find out and suggestions that it becomes 'normal classroom practice' soon if it isn't happening!! The scribe should be someone he knows and perhaps works with already (classroom assistant???) but both DS and the assistant will need practice and guidance beforehand to understand the do and don'ts of scribing. Again, all the rules and regulations are clearly laid out in the booklet I mentioned above.
Another form of scribing which is allowed (which probably doesn't apply to your DS) is that he completes the test and then at the end, he sits with his teacher (and I always make sure that another adult is there as well to cover my back!!!) and they scan his test together and the teacher writes in any illegible words with DS's say so. Again, the form has to be filled in and attached to DS's test. This does not need to be applied for to the LEA.
He will definitely be entitled to work either in a room alone with supervision or a smaller working group - the school just needs to have something documented and filed as to 'why'. Eg teacher has a bit a paper next to her saying MRSF's ds in separate room due to concentration problems. He needs as few distrations as possible (see IEP).
Even if he doesn't get extra time awarded, he is entitled to 'rest breaks' (made much easier if in a separate room). This takes the form of the clock being stopped and simply re-started again so that hae gets the full time that is allowed to him. This does not need to be applied for, but as with the separate room thing, the teacher needs documentation as to WHY.
The music - I haven't done this before so it is something that you will need to ask the school directly. They may need to ask their 'Assessment Link Advisor' at the LEA - the person at the LEA how is meant to know all the nitty gritty about the rules for the SATs.
Have I forgotten anything?
Let me know!
HTH