As someone who grew up with ADHD managed by stimulant drug therapy since age 7, I can earnestly say that my experience was that ADHD drugs did boost my grades and were a crucial factor in my career success, to date (and still are).
At least, as written, the article talks about something different from the study. The article says "However, a growing body of research finds that in the long run, achievement scores, grade-point averages or the likelihood of repeating a grade generally aren't any different in kids with ADHD who take medication compared with those who don't. "
It then says "A June study looked at medication usage and educational outcomes of nearly 4,000 students in Quebec over an average of 11 years and found that boys who took ADHD drugs actually performed worse in school than those with a similar number of symptoms who didn't. Girls taking the medicine reported more emotional problems, according to a working paper published on the website of the National Bureau of Economic Research, a nonprofit economics research firm."
Nowhere, does it say they study studied kids with ADHD, only kids taking ADHD drugs.
I could entirely believe it does not improve grades or cognition in students who are not actually ADHD, but believe it "helps them focus" or whatever.
THe article seems to mix up these things all over the place, in some cases talking about ADHD kids, and in some cases talking about kids taking ADHD drugs.
If the study really only studied kids with some verified accurate ADHD diagnosis, it would be nice to know that.
While, back when I was diagnosed 27 years ago, kids taking ADHD drugs and kids with ADHD were likely much the same group of people, they haven't been for a long time.