I enjoyed these quotes from a recent article in Educational Leadership;
"If the students are answering every one of the teacher’s questions
correctly,” says Wiliam, “the teacher is surely wasting the students’ time. If
the questions are not causing students to struggle and think, they are probably
not worth asking.” He is fond of saying to his students, “Mistakes are evidence that the
questions I asked are tough enough to make you smarter.” Research
indicates that long-term learning improves when students make mistakes and
correct their answers."