Connected Learning for STEM (CL4STEM) is an innovative project aimed at teacher capacity building in science, technology, engineering, and mathematics involving communities of practice as its component to developing teachers' ability to adopt an innovative approach to science instruction and to implement a novel curriculum. Hence, this study investigated the impact of CL4STEM project mobile communities of practice on science and mathematics teachers' capacity towards piloting curated subject-specific OERs in Nigerian secondary schools and to enhancing subject matter knowledge, pedagogical knowledge and practice for achieving Higher-Order Thinking, Equity and Inclusion (HOTIE) in their classroom. The study adopted a survey research design involving documentary content analysis and a one-group pre-test-post-test design to collect qualitative and quantitative secondary data to achieve the objectives of the research. The population of the study involves all science; biology, chemistry, and physics teachers in senior secondary schools in selected states in Northern Nigeria. Purposive sampling was used to select one newly qualified biology, chemistry, physics and mathematics teacher per subject area from twenty sample schools in the population, thus a sample size of 80 science and mathematics teachers, 20 each per subject but less due to attrition. Content analysis of the science teachers' participation in telegram social network communications was used to obtain qualitative data on their CoP practices. While the Pre-test and Post-test on the teachers' subject matter and pedagogical content knowledge was the instrument for quantitative data collection. The instruments were validated by science and mathematics education experts. Four research objectives and four corresponding research questions guided the study. Descriptive narrative, descriptive content analysis and descriptive statistics were used to analyze the data on teachers' participation in the online telegram platform to provide answers to research questions. The study revealed that online CoP has creditably impacted on teachers' subject matter and pedagogical content knowledge. The implications for continuous teacher professional development policy and teacher education curriculum in Nigeria were highlighted. [For the full proceedings, see ED630948.]