Teachers must meet a variety of students' mathematics learning needs but are often not trained to do so. Little is known about how teachers perceive their efficacy to meet diverse math learning needs. The purpose of this qualitative collective case study was to explore teacher attitudes and perceptions of professional development (PD) and differentiated mathematics instruction for kindergarten through eighth grade in Arizona Christian school settings. This study attempted to fill a gap in the literature regarding content-specific teacher perceptions of PD, differentiated instruction for mathematics, and teacher efficacy. Bandura's social learning theory and the aspect of self-efficacy and the zone of proximal development concept from Vygotsky's sociocultural learning theory provided the theoretical framework. Four questions guided the study with a focus on teachers' perceived effectiveness in math instruction, readiness to differentiate math instruction, PD experiences in the Christian school setting, and use of professional learning communities and job-embedded professional development. A purposive sample of 16 Arizona Christian school teachers who taught mathematics for kindergarten through eighth grade completed a questionnaire. Follow-up focus groups were conducted to triangulate the data. Focus group dialogue was transcribed verbatim and member checked. Data were coded using Dedoose. Thematic analysis identified five emerging themes: contingent teacher efficacy, administrative support, challenges for math instruction, differentiated methods implemented, and professional development experiences in Christian schools. Findings noted the importance of teacher self-efficacy and the need for administrators to provide support with effective PD and intentional scheduling. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]