This achievement unlocks when you finish the three trials to officially become a student of the Academy. This happens just before getting to the upper part of the Academy, and requires having found your staff so you can open the three stone doors.
The first stone door/trial is at the top of the central staircase(behind the gate in the entry hall), and immediately to the right. Can be hard to spot.
The second stone door/trial is high up outside, between the two study halls bearing large plaques inlaid into the floor that speak of the history of the Academy. It's the long, balcony like area where Zak will cower on one end until you reach the other, and will the come running after you. Enter the door, then cross the bridge/walkway and you'll find the door.
The third stone door/trial is found by moving to the right from the first stone door, and climbing the stairs almost all the way to the top where the three golems/guardians/minotaur looking, speaking statues are.