Using the nationally representative sample from the United States in the 2012 Programme for International Student Assessment (N = 7,429 students from 240 schools), I examined the relationship between teacher instructional practices and student mathematics achievement. To account for the multilevel structure of the data with students nested within schools, I used a two-level hierarchical linear model in the data analysis. Teacher instructional practices showed statistically significant effects on student mathematics achievement, even after controlling for socioeconomic status (SES) and sex at the student level and school mean SES and whether the school is public or private at the school level. Furthermore, I found that the relationship between teacher instructional practices and student mathematics achievement varied statistically significantly across schools.