Ah cool. Well I hope it turns out to be useful in practice with your DC. You can get some good ideas by browsing the websites designed for schools, even if you use them just for inspiration and then make things yourself! Another useful shop is Spacekraft. (I love sensory toys, so I know lots of websites.)
Tacal - In my experience, school was hard in the early primary school years (until Year 2), then no problem throughout older infants and juniors, then hard again from Year 7. That's almost the opposite of troutsprout's DS' experience, so I guess it differs!
I think school is stressful when your ability to manage is lower and the demands are higher. In fact, I've heard that's what stress is - an imbalance between your ability to cope and what's going on that you have to cope with.
So I think any school age can be harder or easier, depending how coping strategies vs demands are balancing out. Having simple ways to manage by yourself can reduce stress.
If you'd excuse the example...In younger infant school, I would panic if I needed a poo at school! That meant stressful (post-lunch prime poo time) afternoons everyday! The reason was, I had a specific routine at home, involving an Argos catalogue and wipes, so in the different setting of school loos, I had no idea where to begin! If only someone had realised and found a way to explain a step by step method, my afternoons could have been less worry-filled.
In secondary school, for example, my stress could have been lessened by knowing simple self-care skills like tying my own school tie and again, a simple stock phrase to ask for help would have been useful, especially for things like finding new classrooms.
Ineedmorepatience - I relate to what you say about people assuming your DD3 is fine because she hasn't asked for help. I had that a lot too! Being clear on the next few steps of what was expected of me, at any time, would have been like someone letting the sunlight in - making everything feel clearer and calmer.
Sometimes I've heard of referring to 'Now' and 'Next' as a basic structure e.g. 'Now: Colour the picture. Next: Put it in the tray.' Or, 'Now: Hang your coat up. Next: Sit on the carpet.' Or whatever. As well as explaining what to do, I wonder whether it could be a means of checking whether a child is clear and confident about what to do, by asking them what is now and next. As long as the child was asked in the right way, so they didn't feel as though they were being tested on it!
I'm just thinking out loud. I wasn't diagnosed until my earlier twenties, so unfortunately, I had no extra help at school. But these are the sorts of things I could imagine would have been helpful.