Here are -- again -- some anecdotes from former students (all page numbers from Kandelshine's book):
One day he saw two pupils in the back of the class playing chess. He said nothing, despite this being an obvious infraction of the rules. Suddenly, he screamed at one of them -- who made a blunder -- and explained to him the correct move. (pp. 42-43)And, from a personal interview:
He would insert chess terms into his physics lectures. I remember he particularly 'annoyed' a pupil called Laufer [lit. 'runner'; the name of the chess bishop in German - A.P.] He would think about his games during class and, whenever he recalled a bishop move, shouted: 'Laufer, what happens to a vector when...?'. Poor Laufer had to know the material perfectly for every lesson. (p. 43)
He would solve problems on the board and mumble to himself -- 'that's impossible, I had to play Qd7...' We all encouraged him to play in the Israeli championship since we knew we could then copy during the exams, since he'd be thinking of chess. (p. 20)
Oren walked in front of the class for a few minutes back and forth, holding a chalk, mumbling to himself... suddenly he straightened up, said, 'Well, it's mate!', threw the chalk into the garbage can, and started the lesson.So much, as they say, for theory.