There's a huge demographic of teenagers online, so if you are blogging with helpful information for them, and know that what you are writing is something that will be interesting and relevant, then there's no reason you can't be a blog author.

Keep in mind you might run into some age issues (like if you decide to register with AdSense, I think the minimum age is 18). Other than that, if you set a goal and say "I'm going to update my blog once a week", stick to it, and your readers will know you're responsible and keep coming back!