This dataset focuses on the impact of Continuous Professional Development in Teaching and Learning Mathematics and Science (CPD-ITMS), offered by the Rwanda Quality Basic Education for Human Capital Development (RQBEHCD) Project, Subcomponent 1.2. The provided training aimed to provide essential assistance to teachers in upper primary and lower secondary schools including adequate content knowledge, proficiency in laboratory skills, effective pedagogical methods and proficiency in using technology for instructional purposes. The study targeted to assess changes in teachers' content knowledge and beliefs. The data on teachers' content knowledge were collected from 695 lower secondary and 229 upper primary teachers while data on beliefs were collected from 706 lower secondary and 229 primary teachers. All data were collected electronically via Kobo Toolbox and were analyzed in two categories. The first category focused on teachers' performance, while the second examined their pedagogical beliefs. The discussed data offer insights into teachers' performance and beliefs in mathematics and science, enabling other researchers to reanalyze it based on their variables of interest. Moreover, this dataset serves as a valuable resource for policymakers, educators, academics and other educational stakeholders as it highlights the impact of CPD training on upper primary and lower secondary mathematics and science teachers.