17 years old (my birthday is on October). I didn't repeat any classes. I even started taking classes from college on my senior year of High School. I graduated as an Accounting Clerk from High School (My HS was one of those vocational schools)

18 (really 16 for mandatory education, the last 2 years before college are technically optional)

To be honest I feel this is a better question for college, as in when did you finish college (if you went to college of course); since repeating years and dropping out is much more common in college than high school

I stopped going to school when I was 14. I technically dropped out when I was 16. I later went to and completed college with both an Associate of Business Administration and Bachelor of Business Management.

Birthday is in July, so I was 17 when I graduated.

I graduated at 17 in 1997 before many of you were born.

Graduated at 20 in 2009, i've made troublesome once and repeated once.

AUS:

Primary 0 to 6 - 12 years
High School 7 to 10 - 16 years
College 11 to 12 - 18 years

Al school ends in December

18, although I could have graduated a year earlier if my family had been more stable. My birthday is in October, so I was one of the older kids in my grade. After first grade, my school decided I was advanced enough that I could skip the 2nd grade. So I went from first to third grade. However, after that year I moved to Idaho and they refused to place me in fourth grade, so I took third grade again... so technically I did repeat the 3rd grade but I never went to 2nd grade...

Yeah, you probably graduated just before I was born in September. 

And graduated from high school at age 17.

I guess at age 18 since I started University in '92 right after graduating.

I didn't repeat any grades but quit university after 3 years (got bachelors but not masters) and had a steady job in software development at age 21. Since I still lived in student housing my total living costs were less than 20% of my income. So much disposable income, which I disposed off in PC hardware and AV equipment. (9,000 guilder PC, 7,000 guilder AV receiver, 5,000 guilder 2nd hand CRT projector) No debts to pay off either thanks to government subsidized universities, student fund for all, and extra benefits through my dad's work (university fund) I grew up in the golden age for schooling it seems.