For 99% of teens its a terrible choice, but I don't think its always a bad idea. It depends on the individual.
I used steroids at 19 and I don't regret a second of it. I'm 21 now, and I'm about to run another cycle.
I know this sounds rediculous, but in the process of using steroids, I learned a crap ton about the endocrine system. Im much more involved in research and my body. I found out that I've naturally had low T levels all my life and am now on HRT. If I had not used steroids, I would have never known. (NO, it was not the steroids that caused my low-T) It was learning about AAS that made me realize that 300ng/dl is not a normal T level for my age.
So, depending on the individual, you may or may not be ready to use.
I think that you can achieve great results by having a strict diet and working out the natural route. This will ultimately give you the longest lasting gains, with quality muscle mass and less injuries... However, lets be real, if you haven't worked out all your life and you are 30yrs old, theres no difference in taking steroids at 30 then taking steroids at 19.