Children Learning About Second-hand Smoke (CLASS-II) was a two-arm pilot cluster randomised controlled trial funded by the Medical Research Council, UK. The project primarily aimed to establish the effectiveness of a school-based intervention, ‘Smoke Free Homes’ , in reducing exposure of school children to second hand smoke. Its effect on frequency and severity of respiratory illness, healthcare contacts, school absenteeism, smoking uptake and their lung function, quality of life and school performance were also studied.

CLASS II found that a school-based intervention has the potential to reduce children’s exposure to second-hand smoke. The trial provides key information to conduct a future definitive trial in this area of public health, which despite its importance has so far received little attention.