EVERY STUDENT appears to be in grades 3, 4, 5, and 6. There are certainly no high school students in any of these videos. Again, Mr. Lemov rarely mentions how best practice might vary as a function of age, with one exception: he mentions his "Age plus 2" rule, according to which a student's attention span equals their age plus 2. Thus, according to Lemov, a 12-year-old has an attention span of 14 minutes. Lemov shows no awareness of research demonstrating that girls have a longer attention span than same-age boys, indeed he has no interest in gender differences - which is strange, considering that two of the 14 schools in the Uncommon Schools network are single-sex schools: a girls' charter school and a boys' charter school, both in Brooklyn. But he never considers any of the arguments against single-sex schools, e.g. that the single-sex format teaches students that segregation is OK in public schools. He shows a complete lack of interest or awareness of any gender issues whatsoever.