T o older people, Raven-Symone Pearman is still that adorable toddler Olivia on "The Cosby Show."

But to those of us who have only seen "Cosby" in reruns, she's the wacky, all-American high school psychic on "That's So Raven," the first Disney Channel series to reach 100 episodes.

Now, at age 20, the actress who has simplified her stage name to Raven is stepping into her first serious role in Lifetime's made-for-TV movie "For One Night," airing Sunday at 8 p.m. The already-veteran actress plays the lead, a determined senior in a small Southern high school who integrates white and black proms despite old-school racism.

Though set in Louisiana, the film was inspired by a real-life story that happened four years ago in Taylor County, Ga., between Macon and Columbus.

"It was a challenge," says Raven by phone, while on a break from filming a music video for an upcoming "That's So Raven" soundtrack. "I don't like to take things seriously in my own life, so having to do it onscreen was tough."

Gerica McCrary, the real-life student who fought racism at Taylor County Comprehensive High School, says Raven captured the emotional roller coaster she faced in 2002.

"She's a phenomenal actress," says McCrary, now a junior at Columbus State University. "She's real down-to-earth. I watch the movie, and I still get emotional, with all the chaos, all the changes."

Raven says she felt a personal connection to the story: "It amazed me that this is still happening. But then again, I've lived in Atlanta. People will smile to your face and talk about you behind your back. There is still racism."

Though she's not even of legal drinking age, Raven's career spans three decades. She began doing commercials and modeling at age 2, then auditioned for Bill Cosby's "Ghost Dad" in 1989. Instead, Cosby cast her as granddaughter Olivia on his sitcom. At age 3, she was able to memorize several pages of script at a time.

"I don't remember much of that time," she admits. "It gets worse and worse every day. I'll have to go to the DVD to catch up."

Later, in between stints of "normal" life, she spent four years playing the daughter of Mark Curry's character on "Hangin' With Mr. Cooper," recorded two albums and starred in Eddie Murphy's two "Dr. Dolittle" films.

Then in 2002, Disney came calling, offering her a role as the best friend in a new sitcom. But after watching the pilot, Disney officials dumped the original lead and gave her the spotlight. The show -- which finished filming 100 episodes last month, when the Raven character graduates from high school -- is the top-ranked cable show for girls 9 to 14 years old.

"It's corny, good, family-friendly humor," Raven says.

As a budding business mogul, she's already got a fashion and cosmetics line and sells Raven-themed video games, bedding and even an MP3 player. She also is working on a sequel to the popular "Cheetah Girls" TV movie, in which she plays a member of an all-girl pop group.

Though she now lives in Los Angeles, Raven hasn't dived into the party scene the way former roommate Lindsay Lohan has. She won't even confirm whether she's dating anyone, much less whom.

Nor has she adopted Lohan's stick-thin look. She's lost a couple of roles because of it, but she's OK with that.

"I'm healthy even though I'm not a size two," she says. "I'm not on the cover of fashion magazines. But I know when I go out, the mothers come up to me and thank me for being a good role model for kids, for girls of all sizes."