Nelson Dane was feeling annoyed with the subject assigned to him. And he is furthermore irritated with the quality of students he has to teach. So much that his spectacled brown eyes show all his current feelings.
Not that he is boasting, but him teaching these kids is a great boon to them. He is after all a man with great achievements in the field of summoning. So he is confident to guide these children to be greater compared to the rest of their age group.
But really these children are too weak for his standards.
He purposely made the students stay in the room with the least instruction to see their characters too. If one has a distracted mind and petty heart, as a teacher he has to take notice of it to the latest he can. Those characteristics are dangerous in summoning a lifetime companion.
With ample preparations, he can slowly guide the child into a much more stable mindset. Not only for their own good but also for the rest of the school itself.