<qa>  What was the study protocol approved by?The study was a group randomized controlled trial. Within each school Classes of high school students were allocated by randomization to the intervention or control group by a function Randomization in Excel 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, received information about the program and the study and were choose whether to provided informed consent or not. 