Grade D Meat
A student volunteer in the school cafeteria was helping unload a delivery truck when he noticed a case of meat labeled, "USDA Grade D -- Not for human consumption -- Okay for students, criminals, and prisoners of war." There was also an expiration date that was several months in the past. When he pointed this out to the lunch lady, she just gave him an annoyed look and continued making meatballs.
Behind the Legend
The United States Department of Agriculture (USDA) assigns a letter grade to every cut of meat it inspects, with grade "A" meat being the most desirable (e.g., fillet mignoin) and grade "F" being the least desirable (e.g., something the cat brought in from the garden). The grades are quite broad -- for example, SPAM and baloney are grade B and head cheese is C.
There is really nothing wrong with USDA grade D meat. All the label means is that the meat comes from the less desirable portions (e.g., lips, skin, hair, sexual organs, intestinal contents) of a non-standard food animal (e.g., horse, beaver, rat, laboratory chimp), and that it is of a color or texture that one would not expect. This is the same meat you would find in a hotdog, fast food restaurant, or hobo jungle.
In the 1980s, it was decided that meat of this kind, when it could not be put to a more useful purpose such as feeding hogs, could be sold for use in student lunch programs. The Congressional order that put this rule into effect is the same one that classified ketchup as a vegetable and public education as education.