Essays / "Write about your last big writing assignment." -Trouble finding answer to topic [5]

I have recently gone back to school 5 years after high school. My teacher has given us the following essay topic to write about; "Write about your last big writing assignment."

Sounds simple enough except I don't remember any of my old assignments. Anyone have any ideas I could write about or somewhere for me to start if I'm just going to have to make up an old assignment?