I've read that employers of high school graduates may require a diploma but rarely ask for and evaluate the high school transcript, or ask for test scores (even students who don't take the SAT or ACT have state NCLB scores), which they would do if they cared about what students had actually learned. Therefore a high school diploma is largely a marker of conformity. Treating it this way may be rational. Dunkin Donuts (to use a Massachusetts example) does not need its employees to solve algebra problems or write essays, but they do need to be pleasant and punctual.

"To see what is in front of one's nose needs a constant struggle." - George Orwell