The adoption of the Common Core State Standards has necessitated a change in the instructional practices used by many mathematics teachers. The new standards encourage problem solving and the development of conceptual understanding rather than rote memorization of formulas and rules. Researchers have demonstrated that formative assessment is a powerful instructional tool that, when implemented properly, can increase student achievement. The purpose of this quantitative study was to determine how mathematics teachers in Pennsylvania perceive the new standards; how they value and use formative assessment practices including involving students in their work, modeling quality work, providing feedback, and providing opportunities for peer and self-assessment; and how these variables are related to each other. The answers to these research questions could potentially guide future professional development for teachers. This study was guided by the theoretical framework of Bloom, Dewey, and Piaget who each stated that a constructivist approach to learning is necessary for student growth. Likert scale surveys were used and Pearson correlational studies were conducted to analyze the data from the 174 respondents. Results revealed that participants were generally not in favor of the Common Core State Standards, and there were few statistically significant relationships between teachers' value and use of the 4 formative assessment practices and their value of the standards. Participants appeared to have some misconceptions about the standards and the instructional practices that support implementation, suggesting a continued need for professional development. Attention to this professional learning could help to promote student achievement.