15 is pretty young but it's good that you're interest in reptiles is high. Serious herpetology usually starts off in University, primarily in veterary schools, but other schools also go into herpetology as well (zoology, animal physiology, ecology, and a few others). None however go that deep into it. This is where your thirst for knowledge comes in; you search out a herpetology club, or a school with one, and spearhead some research experiments in herpetology, and you're off on a pretty good start. (And there's a ton of research to be done, very little is known about snakes in general, as compared to lets say a domesticated animal).
I'm sure a willing herpetology club will accept you as a member even at your age.
When I was around 16 I used to do some tagging and checking experiments just out of curiosity. The area I used to live in Michigan was absolutely crawling with snakes, mostly garters and water snakes, and I used to catch them, cut a few belly scales in a certain way, very gently as to prevent any harm, and mark down the cut pattern in a notebook along with where the snake was caught, species, length, weight, external parasites on the snake, etc, and release the snake where I caught it. The following year, I'd catch a handful of snakes to see which had the cut patterns and compare them to the notebook data. The thing I learned through that was that snakes come back to their same hunting grounds year after year, and that if you happen across a snake at a certain location, and you happen across another simlar sized snake at the same location at another time, most often it's the same snake, and that fully grown (which was relative, and measured by length of the snake) wild snakes generally do not grow all that much. Of course, now that I look back, there are many mistakes I made, and the data only held true for the time period I did it for (3 years), and the area I was in.
But no worries, you've got a lot of time.
-Lemur 6
