Like you I was schooled at a time when ADHD wasn't something teachers were trained to look for, which meant I wasn't diagnosed until I was well into adulthood. Once I actually got treatment it turned my entire life around. I mourn for the years that I lost. I'm certain that there are times when it is over-diagnosed but ADHD is absolutely a real thing. No amount of stimulation, schooling, or parenting can fix a person who has it.