Air quality in educational environments has a direct and significant impact on both health and student performance. This study presents a low-cost environmental monitoring system based on Internet of Things (IoT) technology, specifically designed to measure in real time critical variables such as temperature, relative humidity, and carbon monoxide (CO) concentration across various school classrooms. The primary objective is to accurately identify exposure conditions that may exceed the maximum levels recommended by major international organizations such as the U.S. Environmental Protection Agency (EPA) and the World Health Organization (WHO). The analysis of the collected data, further contextualized through a comprehensive spatial and temporal characterization of the monitored areas, revealed significant variations in CO levels and microclimatic conditions across different locations and time ranges. This strongly suggests the influence of multiple internal and external factors. The findings from this research provide valuable and actionable evidence to support decision-making processes aimed at mitigating environmental health risks within educational institutions, particularly in the current context of international indoor air quality regulations.