Another teacher here (I do some 'reaching' too, but only to get things on high shelves, not as an occupation ). I've seen ADHD kids by the bucket load. In general, the ones who were medicated were 'quieter', and better able to concentrate in a school environment (and hence learn better). If they even went a day without medication, many of them would have meltdowns - they were often upset, frustrated and angry at themselves as they knew they weren't 'right', iykwim. I've also seen the odd 'zombie' out there too, and one child who'd spend all day crying when on medication. So sad.
I've also done a fair few school camps, and sleep and med.s were often not at all compatible. They'd often have to be pulled out to sleep on their own because they'd be awake at all hours and would just annoy the heck out of their roommates.
My fave story was of a boy whose mum didn't want to do med.s and spent a lot of time and effort changing his diet. She'd often come in and tell me some of the things she'd found he reacted badly to, and it wasn't just the 'usual' culprits. Her boy was a different kid when his diet changed. Having said that, when he got to his teenage years, he was much harder to monitor diet-wise (just wanted to fit in with his friends, understandably) and did end up going onto medication.
Lots of parents resist med's when their kids are younger, but often don't do anything else. By the time the problem is addressed, their child has missed out on their education and social skilling basics and finds it very difficult to function at school (academically as well as socially).
I also know that some parents have had to change med.s several times to find the right one for their child.
Definitely seek support too. There are lots of other things you can do to help the ADHD child that are worth trying.