Funding for this research was provided by:
Text and Data Mining valid from 2020-04-10
Received: 19 December 2019
Accepted: 23 March 2020
First Online: 10 April 2020
Ethics approval and consent to participate
: As our study involved human participants, ethical approval was obtained from the competent Ministries for Education (Baden-Württemberg, Hamburg, Schleswig-Holstein and Brandenburg). Participation in the study was voluntary. All participants and parents were provided with information about the survey beforehand. Parents had to sign an informed consent form for their children to participate.
: Not applicable. Data cannot be traced back to individuals. All student participants were instructed to write a predefined code on their worksheets and paper-based tests, so that data was already de-identified during collection.
: The authors declare that they have no competing interests.