Perhaps you have maintained an exceptional GPA or maybe you excelled in school while also working a part time job. Maybe you finished top of your class and received a special award for your achievements. Think of any accolades that you may have received along the way.
"The achievement that I am most proud of, so far, was completing my undergrad, top of my class. While maintaining very strong grades, I was also President of our school's Diversity Club, and I spent time volunteering at the local Smile drive."