For both math and science, the study finds that a shift of 10 percentage points of time from problem solving to
lecture -
style presentations (for example, increasing the share of time spent
lecturing from 60 to 70 percent) is associated with a rise in student test scores of 4 percent of a standard deviation for the students who had the exact same peers in both their math and science classes — or between one and two months» worth of learning in a
typical school year.