It's definitely real, but it's also misdiagnosed frequently. A lot of teachers and school psychologists push for a diagnosis because it's an easy way of reining in hyperactive male students. Probably about 25% of the male population of my elementary school was diagnosed, of which like half took medication.
My elementary school used scare tactics to try to pressure my parents into giving me ritalin, like telling them that I would grow up depressed, with no friends, and would commit Self Delete. None of which happened obviously.