According to Smithsonian Magazine, an Assyrian clay tablet from 2800 B.C. bears a gloomy inscription describing how the Assyrian youth were ruining civilization.
"Our Earth is degenerate in these later days; there are signs that the world is speedily coming to an end; bribery and corruption are common; children no longer obey their parents," the tablet supposedly reads.
The inscription is reminiscent of another that, according to Newsweek, was unearthed in the Sumerian city of Ur (located in modern-day Iraq and founded in 3800 B.C.), which says, "If the unheard-of actions of today's youth are allowed to continue, then we are doomed."
Whether these tablets actually exist is unclear. (Snopes, where are you when we need you?) What matters is that variations of these quotes have been circulating for at least a century, and there's a reason for that.