The purpose of this basic, exploratory study is to examine primary grades (K-2) teachers' perceptions of the self-efficacy of their students in mathematics, whether or not there is a difference in the self-efficacy between students based on their performance, and to gather information about how teachers are differentiating instruction. Forty teachers completed an online open-ended survey. Data from responses was analyzed through a constant comparative process in order to answer the research questions. Teachers indicated that advanced students generally have a higher mathematical self-efficacy than their peers, therefore possibly influencing advanced students' potential for higher academic achievement in mathematics. Additionally, many teachers reported using small groups and manipulatives as vehicles to differentiate instruction. However, the convenience sample and data collected warrants further studies to more closely examine the interaction between students' self-efficacy, teachers' differentiation, and student achievement.