Completely agree @Tempnamechange98765 - if you're not familiar with typical toddlers, it's impossible to know what's fine and what is concerning. In my case, I have a nephew and niece who are older than my older DS, but they live abroad and so I've spent very little time with them, plus they were brought up bilingual from the beginning so I couldn't compare their language development with my child. Also, my exDH has a nephew who is 6 yrs older than our DS, and he has ASD and ADHD, but is more severely affected (is in a special school as he could not cope in mainstream even with 1-2-1). I've known this child since he was 3, and my ex (and exMIL) did fairly often say how he was just like our DS but I'd look at this child and think, well thank goodness our DS isn't like that because he wasn't, he didn't have the overt sensory issues, at least not as a very little child. It made me think THAT is what ASD looks like, my child doesn't look like that, so my child doesn't have it. Of course I know so much more now...
At 10, I actually don't know. A lot of the time I think he's fine, definitely quirky, but at home, or at least when he's around family he knows well, he seems ok. At school he managed reasonably well socially up to maybe yr 4, there were no accommodations in place for him, but then demands got greater, and there were some worrying incidents of impulsive behaviour. He now has much more understanding in school, since yr 5 anyway. He struggles with a change in routine, or change being thrust on him unexpectedly; the issue is he has it set in his head what something is going to be like, then it isn't and he cannot cope. This can be something like a friend not behaving in the way DS wants/demands/expects, or a teacher changing the seating plan in the classroom, or a stranger killing him in Roblox. He's also big on unfairness, and if a teacher does something he judges to have been unfair (told him off for something he didn't do, for example, which has sadly happened quite a bit, I do think they misinterpret his facial expressions) he cannot brush it off or let it go, he'll dwell on it and rage (not at the time but with me later and I am then tasked with sorting it out).
He's definitely struggling socially a lot more now. He has friends, he's always had friends because he's not naturally shy or quiet, he's a bit of a show-off, likes to be in the spotlight, and has cultivated a class clown persona; he'd be the kid who did something outrageous in the playground. So I think a lot of kids would have always been drawn to that, and in the past I'd have said DS doesn't so much have friends as followers. He's got three friends at school and they've been good friends for the past 2-3 years, and he's secure and comfortable in that. It worries me how he'll cope at high school when he doesn't have that, since there's no guarantee his friends will be at the same school. Obviously, when you're the class clown, there's going to be as many kids who cannot stand that as love it, and so he's always had enemies as well. Lately, his teachers (and him) have described major issues with group work, which was not a problem before, but his classmates are sometimes really intolerant to him, critical of his ideas and impatient, which really upsets and angers him, so I'm keeping a very close eye on how all that pans out this year. It's not boding well for high school. He doesn't see his friends out of school, and he has no social activities. He refuses point blank to do anything that could possibly be described as a "club".
I'm in the process of trying to get him assessed for an EHCP, and he's had some assessments already, with EP, OT and SaLT, which all described various issues that will need intervention, so I am having a small but growing hope he will end up either in an ASD base in a mainstream secondary or with 1-2-1 support. He has coped ok in mainstream primary possibly because it started out as a new school, with just 4 reception classes, so very small, and has grown organically the past 6 years. It's now full, and a very large school, but DS has always been in the oldest cohort, and I feel he is "known" there, and feels very comfortable. The thought of him going to some massive secondary, with 1,000+ pupils, terrifies me.
There's definitely more challenges to come that are impossible to imagine when your baby is not in school - if I could go back and change anything it would be that I'd taken the red flags nursery raised a lot more seriously, and sought a diagnosis for DS then. Because when he got to primary, they claimed not to see anything the matter (apart from behavioural, they just thought he was naughty), and then when his academic issues started to emerge and they put him in intervention classes, they still didn't seem to think there was more to it. Eventually that yr 2 teacher suggested I take him to the GP, and that set the ball rolling. But even after that, with the diagnosis, and recommendations from the psychologist he now see an EP and SaLT to determine his support needs, school failed to do this (not only didn't do this but lied to me that they had). Only when DS was excluded did they get the EP in, 18 months after the recommendation. Another year on and he's only now had the ADHD assessment that the EP referred him for, and seen the SaLT. So he's 10 and finally I have an idea, and he's started the medication that could make a big difference, but this should have happened 2 years ago. It enrages me because the past 2 years have been hard on DS, he's got further and further behind, he's more and more aware of his place in the pecking order, he hates being bottom of the class, he doesn't like being lumped in with what he regards as the stupid kids, he's often really unhappy and depressed about school... he attempted suicide in June. Which is not what any parent wants to deal with but it's lit the most enormous firework under his school, and finally things are being put in place.
My advice has to be - intervention as early as possible, and don't let up, don't allow weeks and months to slip by when you're waiting for people to do what they say they will. :)