The different strategies and methodologies used by teachers in their day-to-day activity may have an impact on the academic performance of their students. Indexes constructed to summarize how teachers address different teaching tasks can be used to quantify the teaching activities' associations with academic results. In the IEA's Trends in Mathematics and Science Study (TIMSS) for eighth grade, the same students take both the mathematics and science tests. As mathematics and science are usually taught by two different teachers at the eighth grade, the results may reveal whether the different strategies used by teachers have an effect on the results of their students. The analyses revealed that collegial activities (collaboration among teachers) exhibited more positive associations than negative associations with student performance among countries. Conversely, two other strategies, passive teaching and active assessment, were more often negatively associated than positively associated with student achievement.