Abstract Purpose: School doctors of the Naga Medical Association have been providing smoking prevention and cessation classes for primary and secondary students. The goal of our study was to examine the current state and health effects of second-hand smoke in students’ homes as well as to gain understanding about ways to prevent second-hand smoke. Methods: In 2018, prior to smoking prevention and cessation classes, we conducted a survey about second-hand smoke at home to primary and secondary school students. We studied the presence of second-hand smoke, pre-existing conditions, and subjective symp toms among third-year upper secondary school students at three public schools in the same area. Results: Our pre-class survey had 750 primary school respondents, 679 lower secondary school respondents, and 311 first-year upper secondary school respondents, constituting 94.6%, 89.7%, and 99.4% response rates, respectively. Rates of smoking among co-residing family members were 51.2% with primary school respondents, 49.6% with lower secondary school respondents, and 40.2% with first year upper secondary school respondents. Responses indicated that 65.4%, 73.6%, and 57.6% of smokers smoked within the home, whereas all others smoked outside. In the study of third-year upper secondary school students, we had 696 respondents for a 94.3% response rate. The rate of smoking among co-residing family was 51.1%, with 78.4% smoking inside the house. Among female students, students with co-residing smokers had significantly higher rates of pre-existing bronchial or cough-variant asthma, as well as many students reporting rashes or dermatitis, prolonged cough, throat pain, eye pain, or itchy skin when compared with students whose family members did not smoke within the house. Among male students residing with smokers, percentage of students who contracted colds more than twice per year was significantly higher compared with students not residing with smokers. We compared students with co-residing smokers who smoked outside the home with those whose co-residing smokers smoked inside the home, but we found that those students co-residing with outdoor smokers did not have significantly improved health compared with those co-residing with inside smokers. Smoking among students’mothers was associated with their history of urticaria and bronchial asthma. Discussion: Encouraging co-residing smokers to smoke outside the home is not sufficient for preventing the negative health effects of second-hand smoke. It is necessary to urge abstinence of smoking within or near structures and support smoking cessation. Conclusion:Smoking among co-residents may cause negative health effects on students including bronchial asthma and colds.