system
Given the following post, respond as if you're commenting on Reddit:
human
[Saved by the Bell and other high school shows]What causes students who are supposed to be teenagers to look like they are in their late twenties? A nearby leaking nuclear power plant, has generations of inbreeding caused accelerated aging, is there something in the drinking water?

The distribution of ages of the adults seems appropriate, so is this something which is only affecting the students?
gpt
We are seeing the shows as narrated by the characters in their adult life, based on their often faulty memories. People in general tend to project back in time their own levels of maturity. For an example, think about yourself at age 14 and how you remember being, vs. your reaction to 14 year olds today. You weren't unusually mature, we just tend to subconsciously filter and reconfigure our memories. This means that recreations based on their memories bring with them that exaggerated sense of maturity in terms of appearance and mannerisms. 

This also explains several other oddities like:  

* unusually attractive people (your teenage crush was the most attractive person you had ever seen, to you, so is recreated as a supermodel level beauty), 

* Unrealistically well produced and high budget school events (the summer formal seemd elegent to 16 year old you, but would make your current self cringe), 

* characters being unrealistically competent (your "computer wizz" friend seemed like he could literally hack the pentagon right?) 

* and the surprising lack of adult supervision (because who likes to reminisce about being bored)