This study investigates differential effectiveness of teacher behaviour in relation to classroom composition by searching for the extent to which teachers exhibit the same teaching skills when they teach mathematics in different classrooms within a school year. Twenty-six teachers who taught mathematics in more than one classroom of the same age group of students participated in this study. Quality of teaching was measured through external observations and student questionnaires. Student achievement in mathematics at the beginning and at the end of the school year was measured. Data about each teacher factor of the dynamic model but orientation and dealing with student misbehaviour were generalizable at the teacher level. Multilevel structural equation modelling analysis revealed that all teacher factors had an effect on student achievement. Prior achievement (aggregated at classroom level) had an effect on the functioning of two factors (orientation and dealing with misbehaviour). Implications of findings are drawn.