L.D.
If a teacher advised me to have my son repeat Kindergarten for the reasons the teacher gave you, then I would in a heart beat.
Do not focus on his age. In first grade it is much more expected that you focus and sit still. If he enters First grade and is constantly being reprimanded by his teacher for not focusing, etc. he might start disliking school.
Really I cannot imagine not repeating kindergarten based on his age as someone suggested below. Being emotionally, intellectually and mentally ready for first grade is more important than the issue about him being a year older.
I would rather my intelligent child be mad at me for being the oldest, than him possibly getting poor grades and always in trouble with the teacher because I didn’t hold him back.
As an adult he will thank you.
Trust me! My adult friends and I never talk about how old we were in Kindergarten!