Kindergarten kids, can take time to adjust. To school.
Now, this may not sound encouraging... but often times, with Kindergarten kids.... it takes until Winter Break, for them to get better at it. Or per my kids' school Counselor, it can take about 3 months. For Kinder kids, to get in the swing of things.
Then, after the kids get back to school from Winter Break, there is a big difference, in maturity and ability and about their school routines.
Kindergarten kids, do NOT... get in the swing of things, in just one week.
Nor in 2 weeks. Nor in even 1 month.
I work at my kids' school.
The Kinder kids this year... is very, difficult. Not that the kids are 'bad." But because, their maturity is just, very different from the last year's Kindergarten group. Everyone notices. I do too. And so, the Kinder Teachers... are VERY VERY much, having to, stretch an extra 5 miles in effort... and techniques... and in methods... in order to facilitate and manage, this year's Kindergarten grade/classes. And YES, they are sending notes home to the parents. Even the very seasoned Teachers, who have been doing it for 20+ years... are, strained, at trying to help these kids. Young or old, a Teacher tries, all sorts of approaches. To help their students. As best, they can... or per the School's, curriculum and rules. So keep that in mind.
It is not only, your son.
AND, keep in mind, that MANY of the "young" "new" Teachers... can be and are often, VERY good, Teachers.
I know. I know many of the "new" "young" Teachers at my kids' school... and they are VERY good, with their students. Very impressive.
Also keep in mind: MANY young kids, are full of energy and do well in the mornings. AND they can go downhill in the afternoon. Why? Because by then they are TIRED and/or may not have eaten, lunch. Even if they had lunch time. MANY kids in the cafeteria, whether they have a home lunch or have school lunch... do not, eat, much. Or at all. Why? Because, young kids like that, are SOOOOO busy talking to the other kids and playing around in the cafeteria and distracted, and thus do not eat much. Then before you know it, lunch period is finished. And a kid who has an empty stomach.. they get TIRED and FUSSY and cannot concentrate.