The most realistic TV show about teens is Degrassi. It's on "The N", Nickelodeon's teen programming site, which starts at 6 p.m. If you have small children who are watching Noggin -- programming for younger kids -- you've probably switched the channel at 6.
Degrassi follows a group of teenagers who attend Degrassi Community School. This is a true ensemble cast with no real "star" and with rotating story lines. For example, Ellie may have a main story for three episodes and then, as Jimmy's story takes focus, Ellie is seen only in the hallway or a classroom.
What makes this so good? The actors are playing kids their own age, give or take a year. Which means that we truly see them grow up on TV: they mature, gain or lose weight, change hairstyles and fashion, etc. It's not 20 somethings playing 14. These teens look like teens.
The rotating story lines are another strength. Instead of having perfect main characters who one week befriend a cutter who is never seen again, and then the next week have a new best friend who is playing with guns, etc., or having a main character who has everything happen to her, the cast is large enough so that while things happen to various people its never overboard and it always stays real. No one character is overburdened.
It helps that the cast is made up of a large group of believable teens and that characterization remains consistent. A bullying story lasted over a year, and showed multiple viewpoints: the kid being bullied, the bullies, the kids who did nothing; and ended in a shooting. No one was painted as perfect, no one depicted as only evil or only good.
The "mean girl" can be brutal to friends and enemies alike; but she is also shown as supportive to her brother, who is gay, so when a classmate came out, "mean girl" was the one who gave her support. These are things that last seasons, not one "very special episode."
Degrassi addresses topical issues without going overboard. One character is a cutter; another struggles with stepparent issues; another with an annoying little brother. While the story lines range from "big drama" to everyday, each story line is treated with equal respect.
If you're thinking the name is familiar, it is. Back in the 1980s, Degrassi Junior High and Degrassi High and a few related shows (The Kids of Degrassi Street, a wrap up movie, etc.) told the stories of a ensemble cast of teens going to Degrassi. The link to the present show? In original Degrassi, Spike was a young teenager who got pregnant with a daughter, Emma; Emma is one of the cast in present day Degrassi. The teens of Degrassi Junior High are now the teachers and parents of the current teens.
A word of caution: Degrassi is a Canadian show and Canada is at least a half season ahead of the U.S. This means there are spoilers galore out there. It is a bit frustrating, because the the official site has a ton of "extras" including blogs for characters which give additional information, which is cool... except then it gives away the rest of the season.