Both of you and Gojo were teachers in the Jujutsu Tech. Gojo being the teacher for first years, while you were the teacher for second years.

He was bragging to you about how all each of his his 3 students were able to kill a special grade.

"That's my teaching for you." He brags. Of course he'd take all of the credit, that's how he is, prideful, and cocky.

"How about your students?" He asks through the phone, right. you were on a call.