Long Lectures Are Ineffective

The digital education impresario Salman Khan says students simply don't have the attentions span:

[A 1976 study] detailed the ebbs and flows of students’ focus during a typical class period. Breaking the session down minute-by-minute, the study’s authors determined that students needed a three- to five-minute period of settling down, which would be followed by 10 to 18 minutes of optimal focus. Then — no matter how good the teacher or how compelling the subject matter — there would come a lapse. In the vernacular, the students would “lose it.”