According to the psychiatric party line, ADHD is a mental disorder involving a dysfunction in some as of yet unspecified brain systems involved in sensory and/or behavioral inhibition and control. In the classroom, ADHD children have difficulty following instructions, staying on task, standing in line, sitting in their chairs, keeping their hands and their thoughts to themselves, and are generally disruptive of the educational process and a nuisance to the teacher and the other students. The disorder is treated with the regular application of stimulant medication, which has a "paradoxical effect" on ADHD kids and calms them down.
A few psychologists—a maligned minority—have begun to suspect that the ADHD label is really just a way of dealing with kids who are having an adverse reaction to the mindlessness of formal education and who resist the authoritarian strictures of the classroom environment. Many ADHD kids who can’t stay on task for more than 30 seconds in the classroom can concentrate for hours at a time on tasks they find personally interesting—and the stimulant drugs work precisely because, like other recreational substances, they make things more interesting.
From an authentic human standpoint, it is the non-ADHD kids, the ones who follow the rules without question, the ones who readily take on a posture of passive subservience to adult authority and group conformity, the ones who are able to acclimate to the captivity and the mindless routines of the classroom, who are truly dysfunctional.
Consider a recent study (full reference below) that looked at how the inclusion of an ADHD child impacts the social behavior of elementary children working in cooperative problem-solving groups. The researchers compared the performance of groups that that did and did not include a child labeled at-risk for ADHD. Although the at-risk children engaged in more negative, off-task, and "uncooperative" behavior, the groups that included an at-risk child were more than five times as likely to be successful at the problem solving task than groups that did not include an at-risk child.
The researchers called this simply an "unexpected result."
And in fact the result makes no sense at all if you assume that ADHD reflects mental dysfunction. But if ADHD is simply a label given to kids who refuse to relinquish their freedom and autonomy, kids who can still think outside the box because their thought process has yet to be totally boxed in, then the result makes perfect sense: adding an at-risk-for-ADHD kid to the group should lead to better problem solving success relative to groups consisting entirely of children who are already firmly on the path to becoming full-fledged sheep.
Zentall, S. S., Kuester, D. A., & Craig, B. A. (2011). Social Behavior in Cooperative Groups: Students at Risk for ADHD and Their Peers. Journal Of Educational Research, 104(1), 28-41.