Barrett tearing up the book didn't really cause any loss to William.
William had calmed down as well,it wouldn't be right to annihilate the Pantheon Guild just because of Barrett's personal actions, would it?
Over the years, William had always tried to blend into the lives of ordinary people. From his current standpoint, wiping out the Pantheon Guild would seem a bit extreme.
Having the members of the Pantheon Guild collectively copy the book was a minor punishment. Having them spread the knowledge was much faster than if William had to teach the students himself.
William didn't bother with the Pantheon Guild members anymore and went straight back to school.
The books that Adrian had printed out the night before were also repaired by William. During class, he handed out a copy to each student.
Today, there were still only four students in class.
Seraphina, of course, was there to attend William's lecture.