Speaking as a library manager, it's SOOO tempting to say, 'Serves the school right for being cheap-skates and not employing a proper 'librarian'!' Our school emloys 2 professional staff, and we ALWAYS follow up bad behaviour, call back untidy students, get them to leave mice, chairs, monitors, keyboards all tidy before they leave. The more staff who insist on it, the morethe kids just do it automatically.. It's down to expectations and following up, as ever.
It's false economy trying to self-run either a library or an ICT suite - unfortunately you hear of an increasing number of schools where Heads throw out all the books and think you can just do with computers; how short sighted, Adolf!