That right there is the biggest problem. I think the "brats" hanging around at the mall all day are a very small percentage. The real problem lies in the ones who are apathetic, depressed and just don't care anymore. And I don't think cops will solve the problem for those kids.
I myself had in the range of 25% absence in Upper Secondary, and even more in Lower Secondary. Without doing drugs and vandalising
. And I was actually racking up pretty nice marks, enough for me to choose what I wanted for Upper Secondary/Uni with no problems. But that's not the case with everyone. I just think the image of everyone who skips school as a delinquent needs to go because it's not true.
As for bad parenting, I think that's a big issue. But on the other hand, the options for a single mom to get her 16-year old son out of bed when he doesn't want to are quite limited. At least in Sweden. If we'd had a more strict system of child-punishment (grounding etc. is rarely done in Sweden), then maybe it would make a difference. The question is how much it'd matter if the kids are in school if they have no interest. I know tons of people who were in class every day, but never achieved anything at all.
The simplest way to solve this, imo? More teachers, smaller groups, more flexible schedules. I think that would lead to an environment that would be more welcoming to all, would likely motivate pupils more, and they'd have more support. It's been proven time and time again that teacher-density and teacher skill are some of the most important factors in pupil results and well being. So quit yapping and just hire all the out of work academics with teacher degrees. Would probably be cheaper than the average tax-cuts these guys pull off.