1) You don't diagnose ADHD in younger kids the same way as older kids. The classic tells being fairly normal for the age. INSTEAD what you look for is what ISN'T typical for the age (some examples include: intense concentration... Whether that's positive like reading/helping/etc., or negative or a 6hour tantrum, or running for 5+ miles until their feet are bleeding. Most toddlers have a 15 minute attention span. ADHD toddlers will easily go 2-6 hours in hyperfocus.)
2) A disqualifying factor for ADHD is it only presenting in one environment. Now... It can LOOK like it doesn't in one (phenom environment), but it will still be everywhere else, and honestly, still in the one it 'doesn't'. BUT only present in one (like preschool, but not home, friends homes, sitters, outings, etc.)... Means its the environment not the brain.
3) Only doctors and psych can diagnose. Teachers may suggest an eval, but NEVER a diagnosis.
3.5) I'm ADHD :) :) :) Snd I have an ADHD son. And I can 'spot' ADHD the way most people can spot Ru Paul. But I NEVER say 'Its ADHD'. I say 'sounds like', neon signs, lay money on it being ADHD, if it is ADHD, 'get an eval', etc. Now... I don't look at the scattegorizing, my radar is on different aspects.... But I STILL don't say 'Is'. Because a LOT of stuff needs to be ruled out first AND disorders share symptoms. Granted, I've yet to be wrong IRL, yet. But I'm not qualified to DX. Just eminently qualified to 'spot'. Teachers, to a degree, are similar... In that they know how an average/typical child 'looks'. So they can say EVAL!!!! But saying ADHD eval is crossing the line. Maybe well intentioned, but still crossing.