1993: Saved by the Bell: The New Class
Character: Megan Jones
Character's age: High school student, 15-16ish.
1996: Sister, Sister
Character: Rhonda Coley
Character's age: She went to the same school as Tia and Tamera.
1998: The Steve Harvey Show
Character's age: One of the students who attended the school where Steve Harvey's character taught.
1997-1998: Buffy the Vampire Slayer
Character: Kendra Young
Character's age: She became a Slayer after Buffy died briefly in Season 1, so she was probably around the same age as Buffy (16 or 17).
1997-1999: Smart Guy
Character: Shirley and another character named Tracy
Character's age: Both characters were high school students who went to school with Mo and Marcus.
1999-2000: Dawson's Creek
Character: Nikki Green
Character's age: She plays a student director who enters the same student film festival as Dawson.
2001: Save the Last Dance
Character's age: The ex-girlfriend of Sean Patrick Thomas' character, who attends the same Chicago high school as Julia Stiles' character.
2009: The Secret Life of the American Teenager
Character's age: Technically, in Secret Life Bianca Lawson plays a 23-year-old who is only dating a high school student, who she then dumps for being too young.
2009-2011: The Vampire Diaries
Character: Emily Bennett
Character's age: It's unclear exactly how old Emily is, but she's part of a family line of young women who are witches, so it's safe to say she's teenage-ish.
2011: American Horror Story
Character's age: She attends Westfield High, the high school where Evan Peters' character goes on a shooting rampage.
2010-2012: Pretty Little Liars
Character: Maya St. Germain
Character's age: Maya dies in Pretty Little Liars at the age of 18.
But it looks like the curse may be over because in Teen Wolf...
She plays Ms. Morell.
Character's age: A French teacher and guidance counselor at Beacon Hills High School. Hooray!
And if you were wondering, Bianca Lawson in real life is 34.
(Bianca Lawson's inability to age was pointed out most expertly here.)