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-month 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, shall receive information about the program and the study and shall be asked to provide informed consent.