Now that I remember well, I started shaving when I was 12 (when I was in 6th grade). I'm an early bloomer, I've always been taller and more developed than other kids my age (well, did used to be the case in early high school .. Everyone around me is pretty much developed). In 7th grade (in the basketball team) I was one of the few guys with hair in their armpits, and when I was in 8th grade I had the hairiest legs on my class (lol, we did check hahahah).
Trick question, I kept a beard from the time it started growing until my late 30s. I had to shave it off a few times in high school, my sister's wedding etc., but can't remember just when it started to grow.
Also, I understand the whole "safety" element of giving new shavers blunted (safety) razors to use, but geez ... I had patchy weirdness for the first few times, as a new razor is actually safer than a blunt one by virtue of its smooth and complete cutting ability.
When I was 16, I decided to let my beard grow down to nipple level, ala ZZ-Top. That was the year I discovered sports bars as a viable hangout. Before you get the wrong idea, I just wanted to go have a glass (or pitcher) of beer, and unwind a bit. There was no drunkenness involved.
Just before I turned 17, I decided to shave it off for senior pictures at high school.
Now I compromise and keep a goatee that's between 1/4" and 5" long, depending.
Long story short: late in my 12th year, hence my selection.
13-14? Holy crap! I didn't shave ever until around 17 or 18 and even then I had a bit of blonde peach fuzz that came back after a couple of weeks. I didn't start shaving every week until about 20-21, and I didn't start shaving every day or two until...last year
Most of my facial hair is still blonde, so I can get away with a few days before it's noticable.
I was 15 I think. I should probably have started younger, 13-14 bracket, but I really didn't like it. I have an electric razor that really hurt and left marks but my parents just thought I was using it wrongly so I had to carry on with it. I also didn't like the idea of shaving - made me feel old. I went into puberty early and until very recently I have been really uncomfortable with the whole topic. I didn't want anything to do with it. I use a wet shave now and I need to every day unless I want a big bushy beard.