Hmm, mine was a lot more recent, maybe two or three years ago (unless you count essays, since I honestly don't remember the first time I wrote one, or a poem, since I wrote an edgy one about the environment when I was like five or six years old).
Anyway, there was this school assignment (that wasn't worth shit ofc, but I don't know if there's a term for that) where we had to write any story we wanted and were granted complete freedom to write what we liked. So I wanted to write something about a mage in his last test before ascending to wizardom.
Of course, I didn't have enough time and ideas to write a full story like that in a single class. To be honest I don't remember what happened, so I probably didn't even give something to the teacher.
If the poem counts, I still have it somewhere. I even won some contest in the classroom and had to read it in public for an event. Unfortunately, no one understood shit of what I meant by that, not even myself. My teacher was like "No, that's not how you read it." So I left the school very confused that day. In fact, I'm still confused about that.