A principal boasts that he spends two hours a day in classrooms. And it is true--he really does visit his school's 17 teachers daily, chatting with students and occasionally chiming in on a lesson. But when teachers are asked what kind of feedback they get, they say the principal rarely talks to them about what he sees when he strolls through…

Teacher evaluation is problematic because it combines two conflicting tasks: improving instruction and judging performance. A Boston elementary principal gradually devised an informal supervision/evaluation system involving brief, random, and frequent classroom visits followed by praise, affirmation, suggestions, and constructive criticism. Even…