I suppose my son must just be fiddly then and have a teacher who wants to make her life easier.
Oh FFS! The teacher's job is to teach, the children are there to learn. If you have a fiddler in your class it can be incredibly distracting for everybody.
The child who fiddles directs their attention to the plaits of the girl in front; the velcro strip on their shoes; something that catches their eye on the floor underneath a cupboard 6 feet away; picking their nose; pulling on someone else's cardigan... And it there's nothing to fiddle with they get fidgety and often start shifting their position, inadvertently kicking someone else in the process.
All the while they are not listening and so they are not learning.
They are distracting the other children so they are not listening and they are not learning.
The other children provide a constant stream of "Miiiiiiiiiissss, Jake kicked me"; "ugh Miss, Jake's picking his nose"; "Miss, Jake's found a paperclip under the cupboard"; "Miss, I don't want to sit next to Jake, he's annoying me".
The teacher can respond with "Jake, I need you to put that down"; "Jake I need you to listen"; "Jake come and sit by me on the carpet" or "Jake, I need you to go and help Miss Smith (the TA) get some things ready" to just get Jake off the carpet and stop him from disturbing everyone else's learning but also interrupting his own.
Jake can end up be subject to the discipline steps from the behaviour policy and find himself losing playtime/golden time/in time out.
Jake hasn't learned anything, his classmates haven't learned anything and the teacher hasn't taught anything. Jake is upset, his classmates are annoyed the teacher is exasperated.
Or the teacher can let Jake hold a small small of blu tack while he's sitting on the carpet. His need to fiddle is met, the teacher can teach and all the children (including Jake) can learn. Harmony in the classroom is restored.
OP, Jake is your son.