[DanTheMan :P]

Hai
For starters, I'd like to say I haven't told anyone either, so I see how you feel in that respect.
But anyway, lets start with going out with short sleeves. I do it. So what is you have scars, everyone around you knows nothing about you, and you are likely never to see them again. Who cares if for one, fleeting moment they saw your scars. All of the times I've been out, no one has ever said anything about them to me. If you are going out with friends who don't know, I just drape a jacket over my arm

But if you ever did decide to tell your parents, I think its the right way to go. 99.9% of the time, teenagers think parents will freak out and they react in the opposite way. I know someone whos friend told his parents. He was panicking until he got home, where his parents just actes calmly, asked him what was wrong and if he wanted to get help. He said soon after he didn't remember feeling this happy since he told them, as he didn't have to hide it any more.
As for things like jobs, chances are you should wear a shirt to an interview anyway, and if you are employed they won't change anything because of your scars.

Finally, there are certain medical methods of removing scars, you could always look into that, or something like bio-oil to reduce their appearance.
-Dan