I agree it sounds like this is a good time to get some testing to see what is really going on. There are a ton of possibilities besides ADHD. It's inappropriate for a teacher to be telling you that your son should be on meds. This is something I might complain about to the principal.
There are many other situations that can look like ADHD. A kids who is just gifted and bored, or one who has a learning disability, or one who is 2E and has both. 2E a gifted child with a learning disability could explain low test scores in a child who otherwise seems gifted yet distracted and unengaged in learning. Figuring out what is going on while your son is young is a good idea. I would probably go with a good outside psychologist that tests for giftedness if you can find and afford it.
Good Luck.
