Received: 12 July 2018
Accepted: 18 January 2019
First Online: 30 January 2019
Ethics approval and consent to participate
: The South African Medical Research Ethics Committee granted ethical approval for the study. Permission was additionally obtained from the relevant Provincial Departments of Education and school principles to use the schools as initial points of contact. Participants, as well as the parent/guardians of participants younger than 18 years, gave written consent and assent to participate in the study.
: Not applicable.
: The authors declare they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.