After going through and reading through the WHOLE thread, I have more to add.

I was a C and D student in HS, and I could never get myself motivated enough to commit to doing well for more than a few days at a time. Leaving school gave me the time I needed to work for a few years (In a hobby shop, which I loved) and find for myself when I was motivated enough to really commit to school. Now I'm doing much better.

Most prospective employers don't care what you did in high school. If you have a certification or an AA, that's what they look at. According to my mom (when I was stressing about not getting the best of grades in college) they don't give a hoot what your GPA was in college either.

Follow your heart, if this job looks like a great long-term prospect, do it. It sounds like a great experience.