Is my body fat percentage okay?!

Alright. I'm almost 15, and I admit I'm not exactly the most athletic guy your gonna find. I have lost a lot of fat in the past 8 months though, thanks to the gym and eating better. Two days ago, I got checked for my body fat percentage by my personal trainer, and it was 17.8%. I've tried looking up on the web if that is reasonable considering my age but I can't seem to find it. My trainer thought it would be good to get me down to about 15%. Is this reasonable? Or am I fine the way I am. I still have a little belly fat, but compared to a year ago, it's almost gone.