That's very insightful @uneazy , thank you.
This is how I view that situation, not to be argumentative, or anything, other than to show how we perceive things so very differently.
DS can't control his shouting out. He can't change that. There are 20 other students in the class who he is disrupting when he does this, and the teacher does not have the resource to, and neither should focus solely on him. Each child is as important as he is. So he gets sent out. As any of them would if they did the same. He doesn't get reprimanded, how another child might, because the teacher knows it's not his fault, he's asked to take 5 minutes to stand outside. He does. He's doesn't like it. He's older now so he's embarrassed too. But he does return calmer. So, who does it benefit? The teacher, who can restore some flow to the lesson for the other 20 children. The other 20 children, who now have an opportunity to answer. And DS there are pros and cons, because he is embarrassed, but ultimately calmer after taking that break and returning.
Whilst he can't control it, it is bad behaviour/manners. The other children can't do that either. They can stop themselves though. DS can't, and so he's asked to take a break. I truly don't see that as discrimination for having ADHD. There's a balance between making allowances and adaptations, and allowing him to affect the rest of the classes learning detrimentally. Yes it's shit. But I don't think it's discrimination. I think if he was given a right rollicking and sent to the head, as if he'd been deliberately obtuse, then that would be unfair, but he's given a couple of "settle down" warnings, and then asked to take a break.
He misses 5 minutes of the lesson. But equally, the rest of the class have missed the previous 5 minutes while the teacher has to deal with DS.