We only figured out inattentive ADHD was a thing in Year 5 or 6. And we put off doing anything about it for a while as we didn't want to medicate. It took DS asking us to explore medication options to get a bullet up our ass (well, DH was the anti medication person so as soon as DS expressed it himself, I leapt into action).
The main difference with medication is that DS finds it a bit easier to focus and concentrate. In Year 7, he got endless codes every day for being distracted for not getting on with things for missing things etc. for example, he is at an iPad school - the number of times he would not manage to get his iPad open and on the right page were uncountable. The teachers mostly knew he wasn't being annoying on purpose, but nonetheless, it drove everyone crazy and even with them being lenient, he still got into trouble a lot.
At his first secondary school parents evening, the feedback we got from eery single teacher was that getting DS to start a task is a real challenge and that in a 55 minute class, he is losing up to 20 minute of work time as he faffs about. He wasn't distracting others because he's not hyperactive and he's not loud etc, but he just couldn't get himself together. His executive function is poor anyway (possibly combo of SPD and ADHD) and it's just a nightmare.
Similarly, homework! In year 6, they used to get a homework booklet that had to be done over 2 weeks. Each section would be given a time estimate for how long it would take - eg the SPAG would be an hour, literacy 90 minutes, maths 1 hour. I remember saying to his teacher in despair that this didn't help me at all because from when we started trying to get DS started to when we did the first question could take an hour and then everything after would take ages too. That continued into Year 7. Now he manages to do his homework in roughly the right amount of time. (Our next job is to work on the QUALITY of the homework
).
even with sports he likes taking his medication if he's got a match on a weekend as he finds it easier to concentrate and stay on task and less likely to be distracted.
I have heard people say that once their child ws medicated suddenly they really did well academically. Im' not sure that we're going to see that level of magical success, but even just after 3 months we are seeing improvements. His targets at school are quite low as they're based on Year 6 SATS and Year 7 assessments, but he's already meeting or exceeding those targets for the "easier" subjects. His first report in November overall saw a small, but notable, improvement on his year end report for Year 7.
Good luck. I think it's a huge journey getting on top of all this but it is worth it.