In fourth grade, I hand-wrote a two-page 'book' about being trapped in a house with a large angry dog.
In tenth grade I wrote a fifty-page novela as part of a school project, which to this day remains the second most embarrassingly cringe story another person had seen. The central problem was that I was trying to write a serious fantasy story about the fate of the world, in the vein of Wheel of Time... but because I was a fifteen year old, all of the major characters were around that same age, and acted like it.
For one example out of many, the main villiian, a golem-making prodigy with ambitions to conquer the world... is an angry horny fifteen year old fuckwit with a sheepish crush on his second-in-command, a sorceress femme-fatale and also a fifteen year old fuckwit. I was mostly oblivious to how absurd and/or disturbing this was until I grew up a bit, tried re-reading it for the nostalgia trip, and decided to burn every copy I could find.
I got a B-, by the way.