Nowadays the average age is high school, and probably trending to grade school
These are the people who are influencing the Google search user at large now.
We’re fucked
When I created my account more than a decade ago, I felt most people knew more than I did about the world. Now almost in my 40s, and there is the definite feeling that the average redditor you're replying to is a white, 16 year old American boy. The apex of civilisation indeed.
Though the original definition seems to be about ISPs giving unfettered Usenet access in 1993, causing a similar flood of newbies everywhere.
Have you ever seen one of the site surveys that subreddits typically do? The median age is almost always above college graduation (22 years old), at least for the subs I frequent. I could see the front page subs having a median in college age (18-22), but I'd be really surprised if it was below 18.