Gosh you must be reeling. Most parents have to fight for a diagnosis or it can take a couple of years so it sounds like you are doing fairly well. However as you have seen post diagnosis support may be minimal. It took 5 months for our letter to arrive, so as others have said get in touch with the SENCO to arrange a meeting with them and the class teacher. Don't wait for papers.
After that however, it is anyone's guess as to what will happen as it will totally depend on your class teacher. We had only suspicions (no diagnosis) when our DS started school. Nursery clearly had suspicions (noone said directly tho) and they recommended extra settling. I did that by getting photos of the classroom and showing them to DS over the summer. You might be able to do this via office staff over the summer if you phone up.
Our DS' transition into school was pretty good - but he doesn't have issues with noise. If your daughter is bothered by loud noises buy some ear defenders straightaway. If she is bothered by smells then consider asking for somewhere she can eat lunch outside the dining hall. Often it is the free time outside classroom where activities are unstructured, that are the times that our kids struggle.
Get yourself a copy of the Incredible Years by Webster Stratton (?) and experiment with the techniques there. Get used to pre-warning of all transitions (that can be anything from 10 minutes to a year for my DS!!), countdowns and visual timetables. You can start the timetables now by getting a free pdf calendar online and stick images on there related to what you will be doing: holiday/home/friends/camping and have school on there too so she sees it is coming and that it will be ongoing.... A daily calendar might be useful for school start itself as she can then see get up, get dressed, breakfast, brush teeth, shoes on, walk to school, school, pick up, home, supper, bath....... etc etc It depends on her particular needs. All kids are different and you just have to figure it out - work backwards from the meltdowns and keep notes to see if you can guess what the source of the problem is... this can take a long time and be for bizarre reasons. Often there are sensory issues - overload or understimulation - in which case exercises (again google is your friend) can help before and after school.
Look up Asperger Experts and use their safe space/quiet time for decompression when you get home. If she is the sort of child who can hold it in at school you will have kickback at home. WE have the reverse, which isn't ideal as without a diagnosis this usually means that parenting skill is brought into question and lots of people suggest trad discipline - which will actually make things kick off much worse.
Really if you have an idea of what upsets her, make a list to discuss with the school. Is she OK with being touched? strong smells? sounds? will she cope in the dinner hall etc?
Aside from this there are some curriculum areas where ASD usually shows up:
- Difficulties with PE - gross motor skills/balance. We have been doing the exercises from Robin Pauc's Brain Food Plan book (none of the food bits tho) and I wish I had found those earlier.
- Handwriting - fine motor or hypermobile fingers. issues with balance making it tricky to sit properly on a chair. Schools seem to show children a font and demonstrate how to make the shape of letters to teach handwriting. There are motor problems which form part of ASD which mean this method doesn't work well for lots of kids. My DS can't watch someone move and then copy their movement. I wish someone had told us about Magic Link earlier. It is expensive but it helped DS immensely. From Year 3 I would also say go for touch typing lessons and ask for a NeoSmart keyboard in class. DS just did a trial and produced 8 beautiful sentences with lovely vocab, spelling, punctuation and grammar - never before seen when he was using a pencil. It's not ideal but the keyboard really reduces the physical burden so they can deal with the cognitive issues of writing stories.
- Disorganisation of self/materials and problems following multi-step instructions. Timetables and planners should help.
- Off task behaviour - probably the core deficit. These kids just can't bring their attention to non-preferred topics - ie the lesson - if it is not of personal interest to them. If find this infuriating in DS. God knows how the teachers keep their cool with it. Our DS is given rewards of computer time to complete his work and he is allowed to write stories on his specialist subject (most of the time) no matter what the class topic is. This works brilliantly now but so far no one at school has been able to explain how this is going to be phased out towards secondary transfer as it's just not a sustainable long term solution :(
- English curriculum - as time goes on written work has to include character, point of view and perspective. Yep - more core deficits.... Amanda Hartington has a nice Aspie-friendly book called I Hate Writing Stories which might be worth a look in a year or two.
- Inability to Self Advocate/Ask for help - instead their issues will come out in behaviour. At best this is uncooperative and odd. At worst it is violent. In the face of bizarre or unacceptable behaviours
it is essential to remain calm and work out what early factors have led to the situation. Sometimes it can be immediately before, other times it is weeks or years. The best way of dealing with it is by good planning - to avoid the problem initially and over time allow slow desensitisation. However I would say that mainstream schools just don't get this, and if they do just don't have the time.
- Social Mistakes - in the early years this isn't too much of a problem with peers. Especially if the teacher is good on explaining differences to the class and that everyone has different strengths/weaknesses/likes/dislikes (our Y2 teacher was brilliant with this and we still benefit from her legacy on this).
Sorry that was much longer than I expected to type. I just tried to run through all of the things I wish I had known 4 years ago. I thought the school would know what to do - but they didn't. I've had to press for every little bit of support. I was told he was too able for an EHCP. So I applied and he now has one with top up funds. I'm really not a pushy person and it's been hard learning to be assertive. On the other hand I have learned so much these past 2 years and met some amazing people. The future for our kids will be good if we can get them the write support - I see my job as getting him through school with as little collateral damage as possible and if I can get him to uni, and into a niche, he will fly. There are a hell of a lot of people at my work who are probably too old to have been diagnosed. They are all successful. The textbooks only cover the bad stories because they haven't had long enough to hear the good ones yet. Good luck - it is going to be OK!