Randomization
The participating students were assigned a study ID number through sorting their last names (and first names if needed) alphabetically and then assigning each student a study ID number. They were then partitioned by simple randomization of their subject ID number within their classrooms using STATA software to either the intervention (air pollution teaching) or control (vaccine teaching) group such that about equal numbers of students in each classroom were assigned to intervention and control groups. The study staff and students were not blinded to the intervention assignment; however, the staff scoring and collecting data from the questionnaires were blinded to the randomization assignment. The data was unblinded by the study statistician who was not involved with the administration or scoring of the questionnaires at the completion of the study.