I left school with pretty average grades, by the time i hit college (college not uni) they really couldn't teach my much to do with IT, so i left, started my own business at 18.
Several years later, with no formal qualifications, i now work as a architect / devops engineer, earning 50k+ a year.
Qualifications will help you get places, but good understanding, experience and a silver tongue will take you further.
Good luck to you.