This study investigated school-based factors influencing the teaching and learning of probability and statistics in mathematics in public secondary schools in Dagoretti North Sub-County, Nairobi County. Probability and statistics are critical areas in the mathematics curriculum that support analytical thinking and real-world decision-making. Despite their significance, students in many schools continue to perform poorly in these topics. The study was guided by three objectives: to analyze the effects of students’ attitudes on the teaching and learning of probability and statistics, to examine the general school culture surrounding these topics, and to assess the availability and adequacy of teaching and learning resources. The research was anchored on the Cognitive Load Theory, which emphasizes the importance of minimizing extraneous cognitive demands to enhance effective learning. A descriptive survey research design was adopted, with data collected from a sample of students and mathematics teachers using structured questionnaires. Quantitative data were analyzed using SPSS and presented in tables and charts. The findings revealed that negative student attitudes, unsupportive school culture, and inadequate teaching resources significantly hinder the effective teaching and learning of probability and statistics. The study concluded that improving student engagement, fostering a positive mathematics culture, and providing adequate instructional materials are essential to enhancing learner outcomes in these topics. It recommends targeted teacher training, investment in modern teaching aids, and collaborative efforts among schools and stakeholders to bridge existing gaps.