Changing classrooms and classes and teachers every hour.
Trying to keep up with the supplies, organizational demands, and the work load that God has not gifted you the tools to deal with that everyone else has.
ADHD kids don't even know where to start. They've got no idea how to deal with any of it. And worse, the shift toward a high-school-type schedule has thrown off whatever routine and equilibrium they'd had built up.
Why is it so hard?
Executive function. It's a fancy name for how your brain organizes and prioritizes projects and tasks. It's the framework most people take for granted in dealing with their day. The alarm goes off, and your average neurotypical rolls over and smacks the snooze, stretches and dozes and works on waking up, then gets up when the alarm goes off again. They wander thoughtlessly through getting dressed, eating, grooming, and getting ready to go. They don't have to think about every single step.
ADHD includes something called executive function disorder. It's what turns a routine into a disorganized mess. Someone with ADHD cannot run on autopilot through their morning--they have no autopilot. Some work around it; others are the disorganized mess running out the door with an armload of papers drooling out of their grip, having lost or forgotten anything and everything from keys to writing utensils to phones to...well, everything.
Part of the problem is that the brain lacks several key capabilities--someone with ADHD does not make sufficient dopamine.* There's less insulation between their emotions and their impulses and their actions than normal people have, because their brains do not reward them for correct actions by producing dopamine. And that "reward" is what helps build executive function in neurotypicals. From toddlerhood.
A lot of people with ADHD lean on waiting until the last possible second to do things, and depend on the adrenaline rush from panic to snap them into focus so that they can do thing things neurotypicals expect to be easy for everyone: things like planning out a draft, planning the steps, estimating the time each step takes, and working slowly, steadily, methodically, and without stress to finish the project.
Without executive function, people with ADHD lack that sense of how long something is going to take. They think it'll take forever, when it might be half an hour or so, at most. So they start out not knowing where to start (and feeling overwhelmed), or how long it's going to take (making it worse), and can't push themselves to get started at all. Literally cannot. They want to. And can't. And if they try, nothing works--their brain goes off in a million directions, with none of them useful.
Parents can provide some framework; parents can teach their kids how to build scaffolding so that they have something external that takes the place of internal executive function. It's hard, though--neurotypical parents don't have any idea how to break down and teach what comes so automatically to them; parents with ADHD may still be suffering from the same problems, and can't help without figuring it out for themselves, first.
Building that framework is essential. Start with the very basic step: what is it you need to do first? Write that down. Then write down what goes next. Build a checklist. People with ADHD can't simply build a routine and get it into autopilot. They have to keep double-checking that list, or they'll get out the door and find they've forgotten deodorant. Or that they didn't get their hair or teeth brushed. Because they got distracted by something else their brain flung at them instead.
Build a checklist for once you get where you're going--work or school. Color code it. Match whatever supplies you need to the color blocks on your schedule.
Build a framework: make sure reminders are visible and attention-catching. Set alarms, use timers. Use bright markers and bright colored sticky notes. If it's out of sight, it's out of mind.
And then forgotten. And not done.
Medication does help, but it isn't a miracle or a cure, and won't build the scaffold. It only lets people focus long enough that they can.
ADHD sucks. It's awful. People with ADHD have to find work-arounds to mimic what neurotypicals do as a matter of course, and they have to work four times as hard to have half of the success.
*Dopamine and serotonin production can be supported, but it's hard to do, and people with ADHD have to be careful. One of the best ways is through diet; one of the most common ways to trigger dopamine production ends up...backfiring. Finding foods that stimulate the production of serotonin can also help with stimulating the production of dopamine, but the issue is that dopamine is also produced by empty, simple carbohydrates--junk food and sugar--because it tastes good, all of which exacerbate the inability to focus, and further damage any executive function abilities.