Received: 12 March 2019
Accepted: 17 June 2019
First Online: 12 July 2019
Ethics approval and consent to participate
: Informed consent was obtained by the students and by their parents.The study was approved by the Directors of the schools, and by the Ethics Committee “Palermo 1” (Chair Person: Professor Salvatore Leone).
: Not applicable.
: The authors declare that they have no competing interests.