ADHD usually needs to be present in more than one setting for any dx to occur, so both you and school would be given a questionnaire (usually SNAP IV) in the first instance to see if further testing was warranted.
School would always tell me Ds was hard to motivate, but as he was bright it wasn't a problem, he could get by and answer the questions without any bother if he put his mind to it.
In year 5 his teacher cut all that short real quick, and kept us there for an hour and quarter, then burst into tears. We went back to the paed, who suggested we pay for testing as the wait list was a year.
He now has, at 10, a dx of ADHD with aspergers traits (social and sensory) anxieties and phobias. (and also a gifted tag).
This has made no difference at all with his schooling. 
except that because we are drugging him, he is easier to keep on task.
Soooooooooo, if school aren't worried, they either still think he is within the bounds of normal, or don't realise how bright he is. They won't (generally) be motivated to do anything about it, without a 'need' presenting. The kids with ADHD who are causing huge disruption int he classroom by throwing chairs and annoying peers will be the priority. If it starts to affect his schooling (or the idiosyncrasies become out of the ordinary as his peers mature - 7yo boys aren't well known for their focus) then he will gradually move into the spotlight as a student who would warrant more observation.
I suspect there is little that school will be interested in at the mo, ESP if he is clever enough to pull off not concentrating. At the most they will put him on the list to be looked at by the ed psych (sometimes around a year wait).
Sometimes parents (particularly of brighter kids) decide they can't wait for referrals and testing through the LA or NHS, and decide to test privately. This means that you can specify you want cognitive testing done as well, and might give you a fuller picture. Some kids have add, some are gifted, some gifted kids have add, etc. the bright kids with add are usually dx later, because they have coping strategies in place (ie they can answer the questions!) in school when they are caught staring into space.
It is worth trying a few of the recommendations to see if add-type interventions work with Ds - wobble cushions, blu tac, fiddle toys etc but tbh if school see no problem they are unlikely to bother. If you are brave enough you can ask about extension work, and see if that will help. Sometimes a child needs both.
It may be that he is entirely within the bounds of normal for 7yo boy. I ran a cub pack. Most of them had add. only two were medicated for it. 7 is the typical sort of age that 'differences' with peers can appear and not be attributable directly to immaturity, but still possibly...
Just ask the teacher, I'd mention casually that he has trouble focusing on his homework. She'll probably smile and say that's entirely normal. You can ask if she has any issues with his concentration etc. I'm not sure I would let on that you've been consulting dr google. At this point you want to flatter her professional opinion. You might want her on side!