Call it benign neglect (or, arguably, dysfunctional politeness, in a way), but should it be a surprise when students take advantage of the non-presence of top administrators--especially the head--to make poor choices? In particular, the head needs to be a visible presence (what Tom Peters, among others, calls MBWA -- management by walking around) so that students have a sense of the moral guidance that s/he offers to the community. When that kind of day-to-day leadership is not seen, students do suffer, and, sooner or later, there will be multiple disciplinary incidents that are a direct result of having no one mind the shop.
If you've ever taken the Underground (the tube) in London, you're familiar with the slogan, "Mind the gap." For schools, I proffer "Mind the shop."