The aim of this action research was to make significant changes to mathematics teaching in a combined second and third primary school class based on the characteristics of high-quality mathematics teaching. A further aim was to improve student satisfaction with the lessons. The changes in teaching were systematically monitored and reflected upon during the study. The recorded lessons were analyzed using the classroom observation protocol. The changes to the lessons contributed to the students' independence, cooperation, and active participation in the teaching process. The students found the lessons, in which they were able to solve mathematical problems, evaluate the results of their learning independently and express their creativity, interesting and motivating. This study shows that changes in teaching depend primarily on the personal commitment, perseverance and motivation of the teacher.