Worksheet secrecy

Edited to mention that this is in Europe, not the US.

Hi! My 3 year old boy has been having trouble sitting for the 15 minutes required by the educators to work on a worksheet. He has even been punished for this by denying him to go outside with the other children and another time he has been denied his afternoon snack because during nap time he made noise (it was the third day in a row that he didn't sleep and he was quiet for the first two days).

They started the year by doing crafts, painting, glueling and modeling, and he got used to doing that. I did do a worksheet with him at home, he resisted at first, but I held him on my lap, and he was able to follow the instructions. He knows all the shapes, can count to ten in two languages, recognizes more than ten letters, memorizes songs and poems easily, can distinguish between one and a group of two objects.

Honestly, I cringe having him sit down to do worksheets. His teachers are of the belief that worksheets and flashcards (sicchida method) are the right way to convey knowledge to 3 year olds. The other thing is that I don't know how the teachers are approaching his social-emotional needs, how they are teaching the children to interact with each other and if they are playing games to foster social skills. I know they do sing and dance and that they play percution instruments once a week.

He was at home for a week due to a cold and I asked his teacher what they will be working on so that I can work with him at home. She didn't say, yet she did say another time that if he refuses to sit down for the worksheets in class, he will be behind on his knowledge.

Is this "secrecy" a normal thing? I feel like parents have a better idea about what their children are doing when they reach school age than when they are in preschool and I find it a bit odd, because 3 year olds are just beginning to learn, yet it feels like a grading system is in place and all must respond to the worksheet/flashcards method of learning, and I was surprised by the lack of feedback in due time. Should I bother to play catch-up, to have him solve the worksheets? Thank you.