> Also if a test is time constrained it's easier to mark. Give a failing student 8 hours and they'll write 30 pages of nonsense.

Sure that makes sense to me, but I don't see why this would not also apply to ADHD students or any other group.

And of course, there needs to be some time limit. All I am saying is, instead of having a group that gets one hour and another group that gets two hours, just give everyone two hours.

I meant "constrained" not in the sense of having a limit at all, but in the sense that often tests are designed in such a way that it is very common that takers are unable to finish in the allotted time. If this constraint serves some purpose (i.e. speed is considered to be desirable) then I don't see why that purpose doesn't apply to everyone.

There can be a genuine need to make it fair. Some students with anxiety can take 10 minutes to read the first question, then are fine. ASD could mean slower uptake as they figure out the exam format.

So let's say you have a generally fair time bonus for mild (clinical) anxiety. The issue is that it's fair for the average mild anxiety, it's an advantage if a student has extremely mild anxiety.

As you say, hopefully the test is not overly time focused, but it's still an advantage, and a lot of these students / parents will go for every advantage they can.