Why wasn't he feeling that much guilt? Because he'd accepted the fact that nothing could be done about it.
No matter the amount of guilt he was feeling, he'd still have to work toward accomplishing the quest. So if he was going to work toward accomplishing the quest anyway, what was the need of feeling that much guilt?
Well, he took his gaze off Dylan completely and focused them on the teacher after the passing of about a minute. He was listening attentively to the teacher's teachings currently.
The teacher was done teaching by now, and she didn't waste time walking out of their classroom the moment she was done.
Murmurings followed the moment she stepped out of their classroom, students began conversing amongst themselves. But it didn't last for long because it didn't take time for another teacher to walk into their classroom, a male this time.