First and foremost, I don't see this as a case of ADD. A child with ADD has problems focusing ALL the time. Almost any child will show those symptoms if they are bored to tears. (I would not suggest phrasing it that way when you speak to the teacher, but you get the point)
I have found that it helped a lot to show the teacher that you are willing to do your part as well. Perhaps ask if you can sent a notebook of extra work to do during down time - you can download tons of worksheets on every subject from the internet, and it only takes a few minutes. I used to send my children with a couple of math worksheets, cursive writing, alphabetizing, and something to read on whatever subject in history appealed to them. It worked well with some teachers, but DS's second grade teacher decided that it was distracting to the other students for him to sit quietly at his seat and write in a notebook - so if you take this route, make sure you ask the teacher first.
Many schools have advanced programs for math and reading. AR is good, although many schools don't do it for kindergarten. DD, however, got special permission to do it in K because her teacher agreed that she was capable. If this is possible, it will give you a good idea of his comprehension level as well. If not, there are other options. Over the summer I told my two to write a good summary of each book they read, and when they got a certain number of summaries done, they got a reward (a trip to the zoo, camping, etc.) It gave me an idea of how well they comprehended the books they were reading, helped them to practice their writing, and encouraged them to read.
Also, ask if your school offers a computer- based advanced math. A lot of schools offer this, but for some reason Kindergarten teachers seem more hesitant than others to use it.
Lastly, ask the teacher if she has any suggestions. Some are horribly opposed to the idea of differentiation, but you never know. Some have fantastic ideas of how to help your child without overwhelming herself. Good luck!
