A mixed-methods study was conducted to investigate the relationship between four aspects of quality of teaching (safe and stimulating learning climate, efficient classroom management, adaptation of teaching, teaching learning strategies) and reading comprehension in segregated, low SES classes in Flanders. Second-grade students (n = 312) were tested for reading comprehension, and their teachers' language lessons (n = 22) were observed. A two-level analysis and qualitative video analysis were conducted. The results show that managing the class efficiently and teaching learning strategies are positively related to reading comprehension, while adaptation of teaching is negatively related to students' reading comprehension. The qualitative results deepen the quantitative findings. They offer insights into the difference in teaching quality of the highest and lowest performing teachers for efficient classroom management, adaptation of teaching and teaching learning strategies. The results and directions for future research are discussed.