In the classroom, a woman in blue was lecturing at the lectern for three students sitting under the podium. The man standing next to him in a hat blew a whistle around his neck, startled the lady and classmates who were lecturing. The woman picked up the blackboard and threw it at the man in the man's hat, and the man in the white cap blew a whistle and made a pause gesture, and rushed to the man in the black hat.