I think the seventeenth-century thug language you're looking for is "'Twere it not assize-time." The contraction at that time was really gangsta.
Oh, right, 'cause no movie villain has ever laughed evilly, right? I don't know if those girls were serious or not but I can't imagine the outrage if something had happened and the principal or other authority said, "Well, we didn't think they were serious because they wrote 'LOL'."
Kids just have to learn that what you type is permanent, public, and open to being stripped of all personal context and used against you in a court of law. Unless we change the current privacy trend lines, approaching digital media this way will have to be as natural to the next generation as looking both ways before you cross the street was to us.