This brief is directed to researchers and adds to the research base about instructional practices that are related to student achievement. Additional evidence on these relationships can suggest specific hypotheses for the future study of such instructional practices, which, in turn, will provide research evidence that could inform professional development of teachers and the writing of instructional materials. The results of this study revealed a pattern of relationships largely consistent with earlier research, but not in every case. Results that are consistent with previous research include increased student achievement associated with teachers dedicating more time to whole-class instruction, suggesting specific practices in response to students' work (1st grade only), using more representations of mathematical ideas, asking the class if it agrees with a student's answer, directing students to help one another understand mathematics, and differentiating curriculum for students above grade level (2nd grade only). Less consistent results were found in three 2nd-grade results, and include lower achievement associated with teachers' higher frequency of eliciting multiple strategies and solutions; prompting a student to lead the class in a routine; and with students more frequently asking each other questions. These findings suggest that practices associated with higher achievement gains include both student-centered and teacher-directed practices; however, some student-centered practices were associated with lower achievement gains. (Contains 11 endnotes and 6 tables.) [For "Instructional Practices and Student Achievement: Correlations from a Study of Math Curricula. NCEE Technical Appendix. NCEE 2013-4020," see ED544192.]