Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Do smaller classes boost achievement mainly by helping teachers impart specific academic skills to students with low academic achievement? Or do they do so primarily by helping teachers engage poorly behaving students? The analysis uses the grade 3 to 4 transition in San Diego Unified School District as a source of exogenous variation in class size (given a California law funding small classes until grade 3). Grade 1 report cards allow separate identification of low-effort and low-achieving students. Results indicate that elicitation of effort or engagement, rather than the teaching of specific skills, may be the dominant channel by which small classes influence disadvantaged students.