Of course we already force children to go to school for 11 years (in the UK). If this community service is such a good idea then it should be done during that time rather than adding another year of compulsion. In my experience young people, when given the opportunity, fall over themselves to get involved especially when the activities involve working helping people. (They are not so keen to pick up litter or clear weeds from parks). Give these activities GCSE equivalent points and all schools will want to join in.

If you are talking about military service as the solution, just think about the proplem first: drinking and fighting. Soldiers never do either, of course.