Honestly I would be careful trying to help to much as you can cause harm. What a lot of parents don't realize is that there is a strong desire to fit in which is just part of being human. With Autism there isn't a lot you can do other than being respectful and generally a good parent.
Also it might be worth examining the family tree. There have been a lots of parents that were diagnosed after the kid. Autism is genetic so it had to come from somewhere.
Thanks for taking the time to reply. These are really good points as I am not particularly good at fitting in myself. I position it as a super power (no peer pressure) but as you say, to a certain degree your child needs to conform.
I think I probably need to learn to be a parent and support as I have taken the opportunity for my wife being a very good mum to slack off myself
I'm a high functioning autistic 33 year old and I can share some of my own experience. The meaning of this post is not to be immediately applicable but more to widen your scope of autism as a whole. Most people are surprised when I tell them I'm autistic, but when people know what to look for they say "I have all the symptoms" which is not 100% accurate.
Most of my social skills I had to learn manually. I felt like I was falling behind socially at age 9 but somehow managed by getting one friend that was always up for playing video games. I recommend explaining in detail facial expressions early, learn how to read body language and then explain it to him.
I'm not sure where I stand on video games since it took me a long time to be able to play in moderation.
Structured activities are the best. Playing board games is really fun and easy way to engage socially with other people(monopoly is really bad, get Catan or other modern games instead). This is why individual sports are very calming such as swimming and athletics suit very well when teamwork could cause friction. Chess is also a nice sport to get into.
One thing you don't want your child to do is to end up masking, "acting normal" takes a ton of energy where you have to be constantly alert of every minor detail in yourself and others since it's not automatic. Focusing on other people only saves a lot of energy, focusing on a single other person is a "solvable problem".
Another thing you should check for is whether you or your partner yourselves have autism. Contrary to popular belief you yourself are very qualified of judging yourself. Be careful though since wording of many tests is written by non-autistic people so answering "I'm not bothered by things that interrupt me from pursuing my major interests." and thinking "Not really, I have a system for that" is not the way they intended for the question to be interpreted.
I had trouble expressing myself growing up until I gained sufficient vocabulary to be able to precisely say what I'm experiencing. Rather than make attempts I stayed silent but giving me time, paper and pen would have helped. I think this issue might stem from me saying something, it being misinterpreted, and then the conversation spinning off in a completely "chaotic" direction.
I have a friend now that's same age that when I say something in a group nobody gets it and he "translates" for me. I suspect he's also autistic.
Autistic people not wanting to speak is not true in most cases. Often in a group it's just impossible to keep up. However one on one many of us can talk for hours about a specific interest.
I'll leave it at that and with a quote from a parenting book. It was aimed at conversation between the parents but it very much applies here also. "What's obvious to you is obvious to you." There is an ocean of things that are obvious to non-autistic people that need explaining. My wife and I frequently have something to like "It's in the bag." In her mind it's "The bag we have been using all day" in my mind it's "The most frequent bag, the grocery bag, the bag she was using, her purse bag and the regular storage bag are all candidates". She's since started saying "The blue bag that's on the counter" instead which makes everything crystal clear in seconds.
Considering it's a big spectrum with all kinds of intelligence and ability levels and other personal things, can you tell a bit more?
Some common things:
In my experience (and those of others I've met) autism often comes with other neurodevelopmental/personality disorders (ADHD spectrum seems to be common).
Often one or several senses are oversensitive (hearing, touch, smell, etc.), so if he or you know what it is you could help to "mute" those sensory stimulations (for example: headphones with music (at a reasonable volume!) to dampen other sounds in the case of sound sensitivity, sunglasses in case of light sensitivity, etc.)
If he's capable of social interactions, try to help him in that. What's acceptable and what isn't, and why.
I think a lot of parents underestimate Autistic children. I don't have concrete evidence to support this but I think Autistic brains develop faster than neurotypical brains. I've seen young children who are knowledgeable on very technical topics.
I'm not even sure at this stage if I can as I understand so little but here goes.
He's what I perceive to be high functioning. In fact most of what they call out I view as being just a little boy. I'm slightly concerned that this attitude comes from my own childhood and whether we establish that I'm also neuro divergent but am keen that I focus on him and not me.
He's bright, good with maths as his mum teaches this. Struggles in class as they're not great at understanding his needs and just see him as wiggly/playing class clown to impress others etc.
He has always had sound sensitivity so people calling that out is interesting to me.
We're working with the school to get better mechanisms in place to support himvand my wife is already amazing at helping him at home.
In my head I need to get onboard too, and transition away from being the typical authoritarian role that a dad may take. I need to understand better what autism is and how to support him
He is also just a 5 year old boy. Autism can sometimes blend in until kids start having more complex social structures. As long as the teachers aren't being abusive school should be fine. I would get him some stim toys so that he isn't being disruptive and can self regulate.