The study is a group randomized controlled trial. High school classes were allocated by randomization to the intervention or control group by a Randomization function in Excel computer program. Outcomes were measured by questionnaire at pre-intervention, post-intervention and 3-months follow-up. The study protocol was approved by Tel Hai College institutional review board. Parents of all participants, in the intervention and in the control group, received information about the program and the study and were asked to provide informed consent.