Conversation so far:
How was Seung-Hui Cho's behavior in school?
Cho looked down and refused to speak when called upon. After one teacher threatened to fail Cho for not participating, he began reading in a strange, deep voice.
How did the bullying at Westfield High School effect Seung-Hui Cho?
Cho looked down and refused to speak when called upon. After one teacher threatened to fail Cho for not participating, he began reading in a strange, deep voice.
Was Seung-Hui Cho a bad student because of his anger?
Cho looked down and refused to speak when called upon.
What was done when Seung-Hui Cho refused to speak when called upon?
One teacher threatened to fail Cho for not participating in class.
Did Seung-Hui Cho participate after being threatened with a failing grade?
He began reading in a strange, deep voice that sounded like he had something in his mouth.“

Question: When did his behavioral problems begin?
Self-contained rewrite: When did Seung-Hui Cho's behavioral problems begin?