Leaving high-school when I was 16 (the legal age here where a student isn't obligated by law to attend). Granted, I didn't do it of my own accord and rather got kicked out because I was already not getting involved in classes or homework.

So I ended up working menial jobs instead, and carried that for several years before I decided I ought to go back and at least get my diploma. That was fourteen years ago.

The delay this caused me in my academic advancement, however, is something I haven't been able to catch up on yet, and now I find myself with a high-school diploma and not much more to show for my experience than low-profile retail, customer service or warehouse jobs.