The purpose of this study was to describe and analyze the perceptions of mother tongue teachers regarding the effectiveness of teaching and various factors that may affect the effectiveness based on a phenomenological approach. For this purpose, ten interviews with mother tongue teachers were conducted. The results show that teachers have clear perceptions of what effectiveness is and use different methods to make teaching more effective. Three extensive categories that affect positively effectiveness were identified: personalized education, teacher leadership and motivation. The findings suggest that there are also factors that negatively affect effectiveness. These factors are teaching time and inappropriate scheduling, difficulty in forming reasonably large and homogeneous groups, inappropriate teaching facilities and lack of collegial learning. The results correspond to the latest research in the field. Overall, the results suggest the variety of perceptions about effectiveness and factors that can affect it.