With my eldest, nursery never had anything negative to say at all until he got to the second half of the final year of Kindergarten (German nursery) and they started to tell me he was being disruptive, but since he had been held back from starting school due to not speaking German, he was a full head taller than all the other children and his legs filled up the entire slide
I felt like he was just bored and this did indeed resolve when he went to school - no more disruptive behaviour reports.
At school he would get middling scores for attention/focus/distractability but because he was academically bright they did not mind this. I remember asking them about ADHD and they said "No, no, I have taught a lot of kids with ADHD, if they have ADHD they can't sit in a chair". Which I knew was not true because I was a child with undiagnosed ADHD, and I never had issues with getting up out of a chair when I was supposed to stay in it.
By third year (equivalent of UK year 4) they had sat him away from a particular friend because they distracted each other in class but this seemed to solve the issue. His teacher also complained about him doodling on his books but I got him a separate notebook for doodling and again this solved it.
Interestingly that was the year that we did the assessment. There was a teacher questionnaire, and she told me that she was very surprised to see that it was for ADHD, but she actually scored him worse than we had on many points. Perhaps because she could compare him to other children his age, whereas we only had our own perception.
In Germany there is no automatic sharing of a child's diagnosis so I have had to inform teachers individually and they are ALWAYS surprised. I think because he is not outwardly hyperactive, at least any more.
OTOH with my 6yo, we have had trouble at Kindergarten since the very beginning. First it took him 6+ months to settle in, then they kept complaining about him not sitting still to eat or not listening to verbal instruction - I just thought this was ridiculous as he was only 2.5, although we did try explaining to him that he must listen to his teachers, and suggested to them that they explain to him the reason behind a rule, as he seemed to respond well to that.
They also said he didn't make many friends or seem interested in other children socially. My husband was the one to find this unremarkable, because he himself is quite introverted.
After a while, he made a friend, which we were pleased about, but then we started getting reports that he and his friend were being disruptive and not listening to adults. At this point he was about 3 or 4 so we were more concerned because most children of that age DO recognise authority of adults. It came to a head when DH went to pick him up and the two of them had thrown a sofa out of the window
We ended up making an appointment to speak to them but it took 4 months for this to actually happen because they were so disorganised. We actually ended up moving both the kids to a Kindergarten closer to home, partially because it was chaotic there, partially because we thought the day (until 4, with an hour's commute) was too long and tiring for him.
He then had his 5 year check up and he was basically totally uncooperative and couldn't/wouldn't do half the instructions the nurse gave him. This had also happened at his 4 year one but they said not to worry. At the 5 year old the doctor picked up on the pattern though and asked about Kindergarten so I told him about the troubles we had had. The doctor said OK - keep an eye for 6 months and come back if he's struggling at the new one.
Moved to the new kindergarten and he immediately did the same thing with a friend. I think he struggles socially to engage/relate to other children, and the only ones that he really clicks with are other children who are high energy, but then they wind each other up and get up to all sorts. It was only about 4 months in the new Kindergarten when they called me in for a meeting because they were really struggling to manage his behaviour. That was the day that I called to self-refer to the psychiatry clinic (which fortunately we can do here) and I made another appointment to follow up with his doctor.
What is interesting to me is that when I asked outright if I should speak to his doctor, both the first and second Kindergarten said oh no, nothing like that, it's fine. But having the benefit of experience and the knowledge of the family history and the fact that even though my older DS was disruptive at home he was not at school, I felt very certain that there WAS a clear indication to seek medical advice. And in fact it's only been since I said to the newer Kindergarten look - we have family history of ADHD and I've referred him for testing for it - that they said ohhhhhh yes that would make sense. (I am actually thinking ASD as well in his case - but we will see what the clinic says.)
We are now between Kindergartens as we have moved but I'm going to be upfront with the new one from the start.
I will say it is SO SO much easier this time around as I am confident in advocating for him and in pointing out where he is struggling. It was nothing like that the first time, as I was constantly second guessing and wondering if it was me. It's horrible and so tough to be stuck there. You are 100% not a failure as you're asking questions and trying things and learning - you are doing brilliantly I promise.