Objective: To analyze the process of handling a pulmonary tuberculosis(TB) outbreak among senior high school students in a boarding school in Chongqing, as well as to investigate the underlying causes of the outbreak, so as to provide evidence to inform TB prevention and control strategies in school settings. Methods: From November 2023 to April 2024, an epidemiological investigation was conducted into the TB outbreak in a grade 12 class from a boarding high school. Suspected cases were screened using symptom screening, tuberculin skin test (TST), and chest X-ray examinations. Confirmed cases underwent individual epidemiological interviews and sputum culture; Cultured positive mycobacterial strains were subjected to whole genome sequencing after identification as Mycobacterium tuberculosis. Results: A total of 10 active pulmonary TB cases were identified, all from the same class, yielding a student attack rate of 16.67%. Three isolates were culture positive, as well as all strains were of L2 type，and the WGS analysis of the strains suggested a common transmission chain. Excluding the index case, four additional cases were detected through symptom driven health care visits. Notably, 70% of patients presented with "chest tightness and chest pain" symptoms, and 50% had "cough" symptoms,but none were detected during morning health checks or tracking of absences due to illness. A total of 326 contacts were identified and underwent three rounds of screening and one follow up examination. In the initial screening, 35 close contacts from the same class showed strong TST positivity, corresponding to a strong positivity rate of 55.56%, significantly higher than the 20.76% observed among casual contacts ( χ 2=29.80, P <0.01). Among the 35 strongly TST positivvity close contacts and five individuals with moderate TST positivity whose induration had increased by ≥10 mm over two years, none received timely preventive treatment initially; five of them were subsequently diagnosed with active TB within three months. Following this, 25 individuals initiated preventive therapy, resulting in a preventive treatment initiation rate of 62.50%. Among TST negative classmates who converted to strong positivity on repeat TST testing at three months, 75.00% started preventive treatment, but only 22.22% completed the full course. Conclusion Inadequate implementation of morning health checks and cause tracking for absenteeism due to illness, poorly standardized screening procedures, and delayed preventive treatment may have been key factors contributing to the spread of the outbreak.