FantasyLover wrote to IC recently, asking her some questions about writing, publishing, and agents (plus, asking if the response could be posted over here)!
...My advice is to try coming through a different door, especially given that you are young and have plenty of time. I would certainly focus on school right now, and when I wrote anything, I would focus on short fiction. It can be first submitted to school for various classwork, and then it can be entered into short story competitions. A good way to amass a book is to write a series of related stories, which can then be used to apply for a mentorship- something you are more likely to achieve having written and won or have even been a runner up in short story competitions...Isobelle Carmody