Middle-schoolers with untreated ADHD are possibly some of the most misunderstood children in school. The assumption of a middle-school teacher is that, if the student had a 'genuine' problem, they would have a 'genuine' diagnosis and a history of attempted interventions and treatments. If your child makes it until middle school before their disorder makes itself entirely obvious -- and some 1 in 12 do! It can be a dire situation if their ADHD is not quickly recognized and understood.
ADHD and the Motivation Problem
One of the most fundamental reasons for this phenomenon is that tweens with ADHD aren't motivated by the same things that their peer group is. The threat of bad grades is simply too far away to be of any meaning to an ADHD child; their brains cannot connect their day-to-day, hour-to-hour behavior with an assessment that happens months later. Because of this, they can come off to teachers like they simply don't care about their grades. This isn't true; they just feel helpless to affect those grades -- they feel like they happen to the student, not like they're caused by the student.
Misbehavior as a Result of Inattention
"Ready, FIRE!... Aim?" -- The classic battle cry of the ADHD tween. Oftentimes, a middle schooler with ADHD has the best of intentions, and they jump into a new assignment with gusto... only to end up getting distracted by the way that Vanessa's hair bounces just so when you kick her chair. Or they'll volunteer to take on a duty that they shouldn't have any problem with, and then simply forget that they had volunteered. Despite the frustration they cause, they're not trying to cause trouble; ADHD simply kicks in to drive the thoughts relevant to their promise (or task at hand) from their mind entirely.
Impulse Control: the Clever Devil
Often, kids with ADHD are smart in unexpected ways; the ADHD brain is known for being highly creative and able to connect subjects along lines that come across as very clever to an adult. Unfortunately, this often plays straight into the idea of the ADHD tween being problematic because it pairs nicely with their lack of impulse control.
The classic example is the teacher saying something negative about an ADHD tween's behavior or the quality of their work, and the child coming back almost instantly (and entirely out of turn) with a biting commentary on something the teacher did wrong or poorly -- not because the child was trying to attack the teacher, but because the ADHD brain connects 1) the teacher and 2) the concept of "poor quality", and simply calls up the last time those two ideas were connected: the teacher's poor performance. And the impulse control problem means that the thought that cropped up immediately comes spilling out their mouth, coming off as a direct attack on the teacher even though it happened practically without any conscious thought or volition on the part of the tween.
Middle school is a place where tweens with ADHD can get along quite nicely with their peers -- but the teachers find it increasingly difficult to keep them functioning normally on both social and scholastic levels.