Danish to English Social Sciences General / Conversation / Greetings / Letters

In a vivid description of an early 20th-century singing class, filled with the chaos caused by disruptive schoolboys, the writer says that they "kastede papirskugler og vidskelaedre efter hverandre eller sloges..." I understand that papirskugler are literally "paper balls," although it is unclear if these were dry wads of paper or the well-known "spitballs" of rowdy schoolboys. As for the second item (vidskelaedre), I haven't been able to find it in any of my dictionaries or any online dictionaries!