The asymmetries of the classroom are intense. With each teacher responsible for a hundred students or more, the typical kid occupies a teacher’s thoughts for—at best—a minute or two per day. But each student only has a handful of teachers. Every instructor looms large in her world, wielding power over her days, via class periods; her nights, via homework; and her future, via grades. She spends much of her time thinking about the teacher’s demands, the teacher’s expectations, the teacher’s preferences and inconsistencies.