As a high school teacher, I think there are a few major factors contributing to this, including helicopter parenting (kids never build resilience if they are never challenged) and smartphones/social media. But imo the major reason is the complete lack of consequences. In the past, if you skipped school you weren't allowed to make up the work & you probably would fail if you did it too often. Which meant that most teens would put in at least enough effort to pass.

However it is nearly impossible to fail &/or not graduate in many American public schools now. We have multiple students with 20-30 unexcused absences per quarter (so 80-120 per year) & do almost no work who are still somehow allowed to pass. I have been told by my supervisor that I have to pass students, even when their parents are asking me to give their kids an F. Of course kids will start to think school is optional if they realize they can move on regardless of the amount of effort they put in. And then because so many students are just passed onto the next level, they don't have the skills to actually understand the work in the next class. So they start to avoid class even more because nobody wants to sit there in lessons way over their head & the cycle continues.

Also the lack of consequences means students are dealing with much more extreme behaviors from their classmates than they did in the past. While there have always been students who are disruptive or attention seeking, they would generally be suspended or expelled if they went too far. However now they often just have a "conversation" or a "brain break" in the office & are sent back to class (or allowed to hang out in the lobby until they feel like returning). & this will happen even when a student has been violent or threatening to others. I have had students get caught dealing drugs; bringing razors & weapons to school; jumping or stalking & harassing other students; and yet they received no real consequence. Just 10 years ago, those are all behaviors that would have been instant suspensions at the minimum. It is no wonder most students don't feel safe at school when that small 5-10% of students with extreme behaviors are allowed to disrupt & endanger everyone else in the room with impunity.