The latest edition of Cartoons for the Classroom features this cartoon by Steve Breen, two-time Pulitzer Prize-winning cartoonist for the San Diego Union-Tribune.
The cartoon shows a man representing the National Rifle Association (NRA) who has just defaced a painting of a teacher standing in front of her class by adding a semi-automatic weapon around her neck.
The title of the lesson is "Taking liberties with someone else's art" (in this case the original painting was by Norman Rockwell), but the cartoon clearly relates to the Sandy Hook Elementary School shooting and the call by the NRA for teachers to be armed (see previous posts on this topic here and here).

