That's been the mantra in the tech world for at least a decade now, and I've grown to really disagree. Managers should have 10 at minimum. Most should have 15-20. They should specialize in being a manager and shouldn't be solving problems except pure management problems. (Good) teachers easily manage classrooms of 10-30 kids, even in private schools. The low direct report count ends up creating managers that have too much power, too much say, and too much time to mess around.