In what may be the ultimate homework project, a 17 year old named Hannah Cairo posted a proof disproving a 40 year old conjecture known as the Mizohata-Takeuchi conjecture. This excellent Quanta article tells the story of how she disproved it.
At 17, Hannah Cairo Solved a Major Math Myster
On February 10, 17 year old Hannah Cairo published an article solving the Mizohata-Takeuchi conjecture.