American students continue to struggle on measures of student achievement. This study employed Hierarchical Linear Modeling to estimate a two-level model and examine the influences of calculator use and teachers' instructional practices on student achievement in mathematics amongst first-grade students. The outcome variable was mathematics test scores from the Early Childhood Longitudinal Study (ECLS). The analysis indicated that students, who frequently use calculators, explain their approach to solving mathematics problems and write out algebraic expressions scored significant higher than their peers. Implications for further research are also shared. (Contains 3 tables and 2 figures.)