This study is the largest report on Mycobacterium tuberculosis transmission rate (TR) from children with pulmonary tuberculosis to school pupils. Higher TR (around 21.6%) was observed in contacts of smear-positive children. TR from pediatric smear-negative index cases was around 0. If our data are confirmed, school contacts of a smear-negative index case could be screened only by clinical evaluation and tuberculin skin test, avoiding the routine use of chest radiographs in children less than 5 years of age as well.