A website for literature help?

Im 12 and i've recently been told by my english teacher that my stories are at a level 7b on the verge of a 7c. Im in year 7 at high school so this is quite impressive. The stories i've wrote didn't take much effort, i actually found it very easy to create them. Is there a site for children my age that will push me to a level 8? I dont want something babyish or to complicated. Thanks