school. All students in selected classes were eligible to participate. The survey proceeded as follows: during July, school teachers were trained to assist students with participating in the survey; during August, the KCDC informed each school about the schedule for conducting the survey and provided certificate numbers for each student; during September and October, students used their certificate numbers to access and complete questionnaires during a regular class period. The KYRBWS was officially approved by the Korea National Statistical Office (KNSO Certificate Number: 11758). Further details regarding the survey design and methods have been provided elsewhere.18
