Being aware of, monitoring and responding constructively to students' signals of motivation and to students' signals of engagement represent two important teaching skills. We hypothesised, however, that teachers would better estimate their students' engagement than they would estimate their students' motivation. To test this hypothesis, Korean high-school teachers rated three aspects of motivation and four aspects of engagement for each student in their class, while students completed questionnaires to provide referent self-reports of these same aspects of their motivation and engagement. Multi-level analyses showed that, after statistically controlling for the potentially confounding information of student achievement, teachers' engagement estimates corresponded significantly to their students' self-reports while their motivation estimate did not. These findings validate teachers' skill in inferring their students' classroom engagement and lead to the recommendation that teachers monitor classroom engagement to be in synch with their students during instruction. (Contains 2 notes and 4 tables.)