Have some sense, finish school you eejit. The world is CRAWLING with young fellas who though they were too smart to finish school when they could be making pocket change. The job market in Ireland is on the way down at the moment.
ps teachers are notoriously poorly paid in ireland, so its probably a bad comparison
"Generally, you will need to have completed your Leaving Certificate. However, if you are applying for a place as a mature student, you will not be asked to meet the usual entry requirements. Different courses operate different entry procedures, but, in general, the colleges will take into account your educational background, work history, community involvement and other achievements and interests. This system is known as the Accreditation of Prior Experiential Learning (APEL). It is useful to find out whether the college of your choice uses the APEL system before you apply.
In some cases, you may be asked to take an entrance exam"
http://www.citizensinformation.ie/categories/education/third-level-education/applying-to-college/third_level_courses_for_mature_students
its not a case of, "ah sure, you may as well drop out, and then get in the back door at 21 with no Leaving". Some colleges won't take you at all, some will require an exam, some will have no Mature Student places in particular courses.
If you can't man up and finish the last year of secondary school, you AREN'T going to like the reality of life as an unskilled labourer.
anyway, you are a scenester, I know this, college will be right up your street.