That's really great for a first attempt at a fugue for someone at such a young age. Have you actually learned or performed a fugue before? They are quite tricky, but once you really get to know the piece of music you will understand more how they work harmonically.
I liked the way you began with a simple subject, makes life a lot less complicated down the track, although I would have liked to have heard more moving parts against it.
Hope this feedback helps, keep up the work!