Introduction: Access to safe drinking water remains a critical public health concern, particularly in developing countries where inadequate sanitation, poor water treatment, and faecal contamination contribute to the spread of waterborne diseases. In Lagos State, Nigeria, limited access to potable water forces many communities to rely on alternative sources that may be microbiologically unsafe, posing significant health risks, especially to school children. Aims: This study aimed to assess the physicochemical and bacteriological quality of drinking water in selected public primary schools in Lagos State, Nigeria. Materials and Methods: Water samples were collected from twenty public primary schools using standard sampling procedures. Physicochemical parameters, including temperature, pH, turbidity, total dissolved solids, residual chlorine and Visual inspection, Colour, Taste, Odour, Iron, Total acidity, Total hardness, Calcium hardness, Magnesium hardness, Chloride, Nitrite, Nitrate, Organic matter, and Salinity, were analysed using standard laboratory methods. Bacteriological quality was determined using the pour plate method for total plate count and the Most Probable Number (MPN) technique for coliform detection. Isolates were further identified based on morphological and biochemical characteristics. Results: Most physicochemical parameters were within acceptable limits; however, pH values were generally acidic, and several samples showed elevated total dissolved solids. Residual chlorine was absent in all samples, indicating inadequate disinfection. Bacteriological analysis revealed that the majority of samples exceeded recommended limits, with 85% testing positive for coliforms. Identified organisms included Escherichia coli, Klebsiella, Enterobacter, and Citrobacter species, indicating faecal contamination. Conclusion: Despite acceptable physicochemical properties, the presence of high microbial loads renders the water unsafe for consumption. The findings highlight the need for improved water treatment, regular monitoring, and better sanitation practices in public primary schools to reduce the risk of waterborne diseases.