There are many factors that may contribute to explaining variation in teacher quality, which is the key to the schools’ success. These factors include not only teacher characteristics, but also conditions of the teachers’ work. This dissertation investigates the relationship between the aspects of teacher professional competence and school environment in their relative contribution to student and teacher outcomes in Sweden and other Nordic countries. Realist social theory serves as an underlying theoretical framework to analyze the meaning of the links between teacher agency and the structures of the educational system. The results demonstrate a positive relationship between the Swedish teachers’ coursework in mathematics, teaching experience and eighth-grade student achievement in mathematics. At the same time, teacher pedagogical skills cannot be easily captured by student assessments of instructional quality. Furthermore, the empirical evidence indicates that job satisfaction of the Swedish eighth-grade mathematics teachers is dependent on the perceived adequacy of workload, opportunities for collegial cooperation, professional development, and student behaviour. There is also support for male teachers’ job satisfaction being more affected by collegial cooperation, whilst student discipline being more important for teachers with low self-efficacy beliefs. Finally, the empirical findings indicate that bullying is relatively frequent in Swedish schools compared to other Nordic countries, and that bullying is also associated with lower student achievement in mathematics. The results imply that, among the Swedish schools and teachers, there are, in some cases, underutilized opportunities to enhance school climate and thus reduce bullying incidents and their negative consequences, such as a lowered student academic performance. Parts of work Article 1. Toropova, A., Johansson, S., & Myrberg, E. (2019). The role of teacher characteristics for student achievement in mathematics and student perceptions of instructional quality. Education Inquiry, 10(4), 275-299. visa artikel Article 2. Toropova, A., Myrberg, E., & Johansson, S. (2020). Teacher job satisfaction: the importance of school working conditions and teacher characteristics. Educational Review, 1-27. visa artikel Article 3. Toropova, A. The role of schools and teachers in creating safe learning environments: A Nordic perspective (Submitted).