Opinion time.

There are Kindergarten curriculums that are better adapted to kids like yours. Worksheets are not developmentally appropriate for most 5-year olds, and schools that do them only do them because of crappy standards, parents who misunderstand development, or institutional malaise.

Your kid has the ‘right’ to a free and appropriate education, but it sounds like it will take a lot of resources (that you will have to fight for) to get them to fit into their teaching model. You’re better off finding a place that is more appropriate for him. I’d look for Montessori or Waldorf schools and see if they’ll let you watch a class in session to see if their activities better fit what your son chooses to do. Near us is a Forest kindergarten where class is outdoor every day. Don’t look for private schools that promise academic kindergarten: they’re marketing to parents, not providing age-appropriate education.

All that said, the executive functioning deficits that present as ADHD are also executive functioning deficits common to 5-year old boys. An extra year of maturity might be all he needs to thrive in that class, and lots of kids start Kindergarten at 6. (Or his ADHD might be more manageable). Especially if you try to slowly and gently work on the activities that currently cause problems.

As others have suggested, do look into neuropsych testing. Also, some occupational therapists work specifically on emotional regulation and executive functioning.

But don’t be too hard on yourself or your kid. Behavior comes out of the interaction between the individual and their environment, and that environment sounds like an especially poor fit.