Cross country question!?

I am a freshmen in high school and am turning 15 in around 6 months. I ran a 18:55 in my 5k race last week. That will be my best time this year because the regional and state meets are very hilly. I was just curious how much can I expect to improve my time by the end of next season. Also should I just keep running the same schedule that I'm on now? Thanks for any answers