The Chosen by Chaim Potok–A question

Question. Late in the book The Chosen, Rueven leads a four day discussion about a Talmud tractate. At the end of the four days, he is asked to stay behind. His teacher compliments him on his work and on his father’s teaching and asks him to NEVER present talmud that way again.

Why?

And why–when Rueven looks in the library and doesn’t find his teachers name anywhere–why does that explain the reason his father doesn’t teach at the yeshiva? (end of chapter 14)