Knowing students as mathematics learners and teaching numbers 10–100: A case study of four 1st grade teachers from Romania

•Teacher knowledge of content and students as mathematics learners varies in accuracy.•Teacher knowledge of students is based on their content knowledge.•Teacher knowledge of students shapes their classroom practice.

Researchers have increasingly linked teacher effectiveness with teacher knowledge of subject matter, curriculum, and teaching. Moreover, teacher knowledge of students has been regarded as another very significant component of teacher knowledge, influencing the classroom practice and student performance. Knowing students as mathematics learners means being aware of the ways students learn certain topics. This study examined the knowledge of students as mathematics learners displayed by four 1st grade teachers from Romania when designing and implementing a lesson on numbers 10–100. Findings show that knowledge of students as mathematics learners influenced the ways teachers planned and implemented their lesson. Teachers learned about students as mathematics learners from one series to another, and they tailored their use of manipulatives and classroom activities to meet the needs of their current students.