*2.1. Participants and Sampling*

Participants were recruited through an official online flatform used by public schools. The flatform is used as a communication tool between the schools and students and all students are able to receive notices from the school through the flatform. For this study, the target population was limited to middle school students enrolled in a public school in Gyeonggi province, the most populous area in South Korea. Participants were a convenience sample of middle school students. Data was collected from September to October 2020. Questionnaires were created in Google Forms and a link for the online survey was distributed through the public school's online flatform. To protect students' rights and improve the quality of the items, the questionnaires were evaluated and refined by experts, such as a middle school teacher. Participants received a \$2 gift card as an incentive, and it took about twenty minutes to complete the survey. A total of three hundred fifteen four students participated. We excluded participants who declined consent to participate, either by themselves or by their caregivers. 26 respondents did not consent to participate so we excluded them in the final sample. As a result, the final sample included three-hundred twenty-eight participants. Even though this study does not contain any private identifiable information, this study was approved by the Institutional Review Board (#200810-1A). Further, given that the participants are not adults, a consent form was provided to both middle school students and their caregivers. Only middle school students whose caregivers also agreed with the participation engaged in this study. In addition, we did not collect any private information such as name, address, etc.

### *2.2. Measures*
