It started as a series of stories in
Superboy and perhaps another title that were continued into the
Superman: The Secret Years four issue mini-series. It covered Clark's experiences in college and how he transitioned from "Superboy" into "Superman." Covers by Frank Miller.
I just read the lead-in story in
Superboy where Clark decides which university to attend, leaves Smallville, and then Perry eventually gets the scoop on Superboy's move to Metropolis after every other major city falsely claims to have him.