Laura Ingalls Wilder & the Savage Child
In "Farmer Boy" there's a section about a teacher who is beaten and killed by teenage students, with the encouragment of their father.
In "Little Town on the Prairie" (when Laura is a teenager in school) and "These Happy Golden Years" (when she's a very young schoolteacher) LIW is forthright about the constant, draining discipline issues teachers had to deal with, for the most part in classes much smaller than the 22-30 students I'd expect today.
On a per-student-day basis, LIW reports much higher levels of student indiscipline and rudeness than would be tolerated today. Then as now, the rude, undisciplined, arrogant problem children had rude, arrogant parents, and neither poverty nor wealth guaranteed good behavior.
Indeed, given that LIW's schools were much less inclusive than schools today (most of the teenage boys didn't go to school most of the year, or at all), I think the evidence suggests that children today are, on average, better-disciplined than in LIW's day.
I do think one of the factors encouraging kids to be rude is that "political correctness" is used as a disparaging term for "respect and consideration for others". I consider it one facet of the "asshole politics" I saw developing in the Reagan era and which continues to dominate the American political scene.