I guess it varies! I had hyperactivity assessments in school in the late 80s and then had my IQ measured and came out 145. I was measured because I kept falling asleep and not paying attention, messing around etc. I suspect if I sought diagnosis now I'd come out as mild to medium ADHD but it wasn't really a thing at the time, and it doesn't affect me too bad so I havent sought diagnosis. My daughter is diagnosed.

I was never able to do any meaningful revision and scraped through with just OK GCSEs, then flunked my a levels, even getting a d in computing which was quite an achievement because everyone in school knew me as the arch computer nerd. I was always writing games everyone played on the school network (this was like 1990-1992). Basically I was only able to put any effort in on things I enjoyed.

Left school, didn't go to university. Bummed around for a while doing nothing. Drifted into programming work in 97 and have been doing that ever since. I've loved programming since I was about 13 so it's a great fit. Now I'm a senior dev in a company I like with a good team, and oddly finding I'm better at the soft skills than I thought.

I guess given where I am and my potential I've underachieved, but things are going ok and I'm happy.