Abstract
One of the foundational assumptions in education is that greater teacher knowledge contributes to greater gains in student knowledge, but empirical evidence in support of this assumption is scarce. Using a U.S. sample of 79 biology teachers and their 2749 high school students, we investigate whether teachers' subject matter knowledge (SMK) and knowledge of students' misconceptions (KOSM) in high school life science are associated with students' posttest performance on multiple-choice test items designed to reveal student misconceptions, after controlling for their pretest scores. We found that students were more likely to answer an item on the posttest correctly if their teachers could answer the question correctly, themselves (SMK). Teachers' ability to predict students' most common wrong answer (KOSM) for an item predicted even better student performance. Items for which a particular wrong answer rose above others in popularity saw an even greater benefit for teacher KOSM.