About 5-10 years I would say a man named Jeffery Thomas created a little drawing of a teenage Joker and Harley Quinn saying "The class clown has never been this funny, or psychotic" In which he later submitted it to DC who loved the idea.
DC then assigned Thomas Jeffery to work with another man named Celeste Green to work on a show called 'Gotham High' a story focusing on all the characters featured in the Batman comics except they where all around the same age attending high school. Instead of dealing with Murder, Crime and Torment they would've been put through Homework, bullying and attempting to talk to the girl/boy you've had a crush on.
All characters where given there on reputation which was as follows:
Bruce Wayne: The rich kid whom all the girls crushed on.
Barbara Gordon: The sexy girl next door.
Edward Nygma: The nerd.
Harvey Dent: The class president.
Pamela Isley: The super hot popular girl.
Victor Fries: The "cool" kid.
Matt Hagen: The art freak.
Oswald Cobblepot: The dorky fat kid.
Selina Kyle: The sexy goth chick.
Bane: The all-star wrestler.
Waylon "Croc" Jones: The star football player.
Jonathan Crane: The punk.
The Joker: The Class Clown.
Harley Quinn: The Juggalette.
Kirk Langstrom: The teacher.
Unfortunately however, this idea didn't go very far, the only thing which we saw was some of the concept art seen below:
Now, I read about this quite a while ago and was always disappointing that this show didn't get very far as I would've loved to have seen a lighter Batman show and I'm not talking like Batman: Brave and the Bold, I'm talking like more Ultimate Spider-Man mixed with Batman: The Animated Series, so I still wanted to see elements of the dark aura that Batman typically gives off but give that slightly more cheerier tone to it as well if that wasn't to much to ask but we will never get to see this as the idea was soon cancels for reasons unknown which is rather strange in my opinion as I believed it was such a strong concept they had but I guess they weren't read to commit.
Let me know in the comments what you think of this idea and if you thought it would've been a great show for teens, and if you want to see more watch the parody trailer for the live action Gotham High TV show labelled 'The Prequel to The Dark Knight Trilogy'