The situation was with a primary aged child on a drama class so no exam results in the equation. In fact that leads to a whole new discussion on the value of exams.
I chose private education for my dd to get away from the tyrrany of SATS for example, I value education at this age, not tests.
But it can work at secondary too, of course the teacher has to be skilled in getting back on track when needed, it is like a trade off, the ADHD child feels like his contribution is valued so is more likely to participate inthe rest of the class.
In my own GCSE year my Geography teacher devoted a whole class to a debate on a topic I had been arguiing the toss about with him.
Was I being disruptive, yes, probably, his way of dealing with it was to say, I am stopping this discussion now, but next lesson we'll do it properly, you can argue one way, someone else another then we have a vote, like a proper debate.
This was in a top set class by the way. And my Geography result, Grade B,not bad considering I am an arts person really. I think the class as a whole did pretty well.