Naa:

It was crafted by a student, Kenneth John Freeman, for his Cambridge dissertation published in 1907. Freeman did not claim that the passage under analysis was a direct quotation of anyone; instead, he was presenting his own summary of the complaints directed against young people in ancient times. The words he used were later slightly altered to yield the modern version. In fact, more than one section of his thesis has been excerpted and then attributed classical luminaries.

https://quoteinvestigator.com/2010/05/01/misbehave/