Received: 16 March 2021
Accepted: 1 December 2021
First Online: 23 December 2021
: Participants’ assent and parents’ written informed consent was obtained before the start of the study. Ethical permission was given by the Human Ethics Committee at the University of Duisburg-Essen, Faculty of Educational Sciences. All procedures performed were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Written informed consent was obtained from all participants included in this study. This study adheres to the CONSORT guidelines for reporting clinical trials.
: Not applicable.
: The author declare that he has no competing interests.