A few months ago I saw a graph showing how many more teens were employed in the 1980s than in the 2000s and 2010s. (sadly I can't find it now)   

I think this trend toward teens working less contributes a lot to the hate everyone piles on teenagers.

Back in the 80s young adults aged 14-18 socialized with older adults sometimes. Maybe with neighbors, their parents friends, during church or scouting activities, while cheering for a local football team, but mostly at work. Usually in the service industry.

Restaurants, and retail outlets had staff aged 16 to 65. They mixed. They got to know each other. They communicated. They learned from each other. In those days NOBODY had an official mentor. But everybody had half a dozen unofficial ones. 

Chatting about the world with coworkers of various ages and backgrounds was Very Healthy for us.   It's so much harder to hate people you've gotten to know.   Fewer teens in the workplace is a sad development. It makes our society worse.