When Mr. Williams means business, he is not kidding around. “He’s pretty quiet, pretty serious,” said Ashabur Rahman, a fifth grader at Glenn Elementary School who has him for math and science, reports the New York Times. John Williams III, 36, is not some jokey teacher. “At the start of the year, some kids said he was going to be the meanest teacher in the school,” said Trajen Womack. Chelsea Parra, heard the same: “A lot of people were saying it.”