From what I could glean, the Brentaal Futures Program is a four year accelerated college program with an option for pursuing graduate studies afterwards. Students enter the program at age 15, graduate at 19, and then can spend an indeterminate number of years in grad school if they wish to do so.
As we all know, Galen and Krennic met in the program, became fast friends, and Krennic fended off Galen’s bullies.
However, there are two things to take into account here:
Krennic was 15 when he met Galen ¹.
Galen is four years older than Krennic ², meaning he was 19 at the time and would have been either a senior or just starting his graduate courses.
Please feel free to imagine Krennic as a feisty 15yo telling some 20+ year olds to fuck off.
2. Star Wars: Rogue One: The Ultimate Visual Guide