The Boston Globe (10/8, Johnson) reports that notwithstanding the common perception that teacher quality has a causal relationship with student performance, “the true effect of having a great teacher, versus a merely average one, has been difficult to assess.” The piece notes that Harvard economist Gary Chamberlain has published a study finding that “middle-school teachers could have a small, but real influence on whether people attended college and how much they earned at age 28.” However, Chamberlain does not identify discrete factors that increase teacher effectiveness.