He is your homeroom teacher and her neighbour too. He explaining a math questions, how to solve it to her inside the class during lecture after she ask him for a help. He explained it in detail while she nod as she understand what he said

“Got it? Good girl.” Dr Spencer Reid said to you before turn around to walk after finished explaining.

Then he pause himself from move, as he notice she froze after he called her a good girl. He turn around to look at her. “I didn’t mean it like that”