Kids that age are naturally distractible. When you add in ADHD — treated or not — they will look distractible to teachers in comparison to other students. Medication helps but it does not completely erase symptoms. He is likely going to need consistent redirection, even if his medication is working optimally.
Is he more distractible the first day or two of the week? When we tried no meds on weekends, every Monday and Tuesday were hell because he was trying to get used to the medication all over again.
Now, the level of distractibility could signal that the medication or dosage isn’t optimal for him at this point. There’s just more investigation to be done before you can come to that conclusion. Work with his prescribing doc to figure this out.