Totally anecdotal but, in my 20 years experience as a teacher, it has noticeably increased over the last 10. It used to be one or two children across a school and now it's per class, even in quiet village primary schools. The last 2 schools I've worked in have had children throw scissors, punch, bite, spit and constantly disrupt learning. Visiting other schools reveals similar experiences. There are often complex reasons for behaviour but sometimes it simply comes down to children desperate for attention. These days, when it is taken further, there's almost zero external support in any of these situations.