No, grade school teachers are generally not qualified, and as a result, they are unable to provide a diagnosis. But a teacher, seeing many students, might recognize the symptoms and refer a student to a psychiatrist, which sounds like what happened here.
YOU are not qualified to determine that the doctor's diagnosis was a rubber stamp.
Are you trained in psychiatry? Do you have a license to practice medicine? If the answer is no, then you are not qualified to determine whether your son has ADHD, or to determine that the doctor's diagnosis is incorrect.
I am "trained" in Electromagnetics. DC to daylight. Fully qualified. It is most interesting you believe that I am unqualified to make any judgement, other than in my field.
I work in an academic environment where I give counsel to doctors in many fields. They seem to have less disdain for it that you do. Although I've run into a few, like the Doctor of Engineering that tried to have me fired because I called him by his first name. Or the one I insulted by correcting an egregious mistake on his part to one of his students. It would have destroyed the student's work his grade, and cost possibly millions. Neither got far. Insecure people with degrees.
Smart people listen to what others have to say. I do. I've asked for and taken advice from the person cleaning the office, or more often from electricians. I gauge if the advice or statement has merit, and accept or deny it based on the merit, not the person's education level. I don't have a doctorates in anything, yet I'm considered a resource among many who do. As expensive as my burn rate was, I was in high demand for different groups, many of which had little to do with my field. For crying out loud, I was a process chemist for a year. So far from my field it was ridiculous. But I did well, filling in and learning until they hired a new chemist. I got the work because I had developed a unique photo exposure and processing method for metallurgy, I supposed.
Now on to these medical experts. I've had 3 relatives killed by doctors. Bad professional Medical Doctor prescription work damn near killed my wife. My mother in law had a TIA, was in the hospital in the ER. She said they had given her a diuretic and she was peeing a lot.
Wife and I were talking to the ER doctor, a nice lady, who told us they were concerned about MIL's strange low potassium levels. I noted that they had given her a diuretic was urinating a lot, which probably caused the low potassium. The ER doctor went wide eyed and blushed. "Oh - yes, that's what caused the low potassium. Thank you!" Stopped the Diuretic, and the potassium levels returned to normal fairly quickly. I am presumably not allowed to note that - except I will, and I am. One does not need a Doctorate to know that potassium levels can get unbalanced when taking a strong diuretic.
The only place where the degree makes a person "correct" is a courtroom, and everyone has their doctors with different opinions. Which one is correct?t. People who are not doctors are on the Jury, casting judgement.
You see my friend, that doctorate (in any field) does not make a person an ubermenchen. The only people who have issues with my judgements and opinions are people who are insecure. the idea that I am someone whois versed in many fields, and sorry, I've been around long enough to know that they are not infallible, and have seen their qualified "professional" mistakes often enough that if they don't want to hear my thoughts - they won't be my doctor. They are not in any way superior. And the smart ones listen. Maybe I'm wrong, maybe I'm right. But determining I am wrong because of my background - that's wrong.