walk in straight lines

"As I have mentioned some of the modern miracles of science and industry," he went on, "you have asked me how men ever managed to achieve them. This anecdote is my answer. . . . They walked in straight lines. . . . Each man had his 'pine tree' in the distance — his goal."

When the principal installed typical no-excuses rules—mandates that students walk in straight lines between rooms or sit in silence if a teacher raises two fingers, for example—the atmosphere of the school apparently calmed and test scores went up.