There are mistakes...and then there are mistakes.
"...A couple mourning their dead teenage daughter were sent a letter by her school two months later blasting her poor attendance.
The note threatened to ban Megan Gillan, 15, from her year-end prom unless she stopped playing truant.
...A school spokesman apologized and told the Manchester Evening News, "that letter should not have gone out," and blamed it on a "software error." (source)
If there was ever an instance that warranted the saying "rubbing salt in the wounds..."