As Debbie Gibson took center stage at Madison Square Garden for her brief set during the Atlantic Records anniversary salute in May, many in the hard- rocking crowd hissed and booed wildly. The concertgoers, who had been waiting more than 10 hours to see Led Zeppelin reunite, were completely out of patience. The last thing any of them wanted now was more perky pop.

“Get off the stage,” many of the seething Zep fans yelled in anger. In fact, they did everything but throw tomatoes at her.

But 17-year-old Debbie Gibson, in her first major hometown concert, ignored it all, then swung into a high-energy five-song-and-dance set that earned a standing ovation. She overcame the hostility with a polished, easy air that belied her youth. Her remarkable poise that night seemed to flow directly from her well-grounded personality.

“I was very proud of that accomplishment,” she said. “It was a big thing for me. I proved I’m not a one-hit artist. And let’s face it, if you could entertain that crowd, you could entertain anyone. Good entertainment is good entertainment.”

But wasn’t she nervous? “Not at all, I’m just a bold person. Really, it was easy. This whole year has just been great.”

For Deborah “Debs The Gibber” Gibson (as she is listed in her high school yearbook), this whole year has actually been phenomenal. And the manner in which she has seamlessly juggled high school, boyfriends, the prom, final exams and her burgeoning career as one of pop music’s brightest stars, is an exceptional accomplishment in itself.

A childhood piano whiz and young star of several well-known TV commercials, Debbie’s now-platinum debut album, Out of the Blue, was quietly released last summer. It attracted little media notice, but radio fans quickly warmed up to her catchy melodies and romantic rhymes.

Then, one by one the hits piled up until Foolish Beat, the fourth single, reached No. 1. With that, Debbie became the youngest artist in chart history to write, perform and produce a No. 1 song.

Out of nowhere, the Atlantic Recording Corp. suddenly had a monster hit on its hands.

Ironically, it was just four years ago, during her freshman year, that Debbie won a pair of tickets to see Madonna. Now she’s got a tour of her own — launched just three days after her graduation from Long Island’s Calhoun High. She arrives at the West Palm Beach Auditorium tonight.

With the chart success of other teen-age artists this year, initially Debbie’s career suffered briefly from a public misconception that she was little more than just another frothy dance star — just another Tiffany. But as her ability to write, produce and arrange her own material became more well-known, her image improved considerably. Critics are no longer dismissing her, either. Her genuine, gimmick-free sound has been among the freshest new efforts to come along in years.

All of this — the critical breakthrough, the recent No. 1 single, the prom, graduation, the date at Madison Square Garden, the new tour — has happened in just a matter of weeks, but Gibson swears it hasn’t affected her. Aside from her almost limitless creativity, she seems overwhelmingly normal.

To celebrate the end of high school, she did what almost every other Long Island kid has done for decades — she rented a limo, she danced at the prom, she went to a Manhattan nightclub afterward, and then to the beach to watch the sunrise. Later, Debbie and her friends went back to her house, where her mother cooked breakfast for all of them.

“A lot of artists sometimes lose all sense of reality,” Debbie said during a recent telephone conversation from her tour bus. “I think you just have to keep your feet on the ground. Anyway, my parents, my friends, they would never let me become obnoxious. I get along with everybody. I do things for myself. I don’t isolate myself. I mean, even though sometimes now it’s like a project for me to go to a movie, I’m not gonna start putting on disguises and acting like a jerk.”

Debbie says she pretty much has the same concerns as any other young adult, although she is not planning to go to college just yet. She did well in school this year, even with 75 days absent, maintaining an honors average by just “staying on top of things. I had a simple schedule, though. Just Health, Spanish and English. You know, it’s senior year.”

For her 18th birthday on Aug. 31, her dream is to return to HotRod’s — the New York nightclub where she and her friends partied after the prom. She also wants to study Japanese, and get her driver’s license.

“I have so many things — everything just running around in my mind — so many elaborate ideas that I want to put on stage — and now I have. I think I owe the people who bought the album a good show. I’m having a lot of fun; I can hardly believe people get paid for doing this.”

In fact, if she does have a pet peeve, it’s that she’s tired of answering questions about “new-found wealth.”

“All the kids at school think there’s this man with a big wheelbarrow who delivers all this money to our house every day. What they don’t understand is that there’s also another man with an even bigger wheelbarrow who comes to take it away.

“I mean, there is a tremendous amount of re-investing that goes on in this business that people don’t realize. Touring and recording are very expensive.”

Traveling with Debbie this summer is her mother, Diane, and younger sister, Denise, 13, who is her wardrobe assistant. Debbie also has two older sisters — Michele, 21, is a fashion design student at Vassar College; Karen, 22, is working for rival Polygram Records after a brief stint at Motown. Her father, Joe, is a customer service representative for TWA.

The Gibsons have always been a musical family. All four sisters excelled in their piano studies from the start. Debbie says she remembers taking classical pieces and jazzing them up, much to the dismay of her piano teacher. “He said he once had another student who did the same thing. It drove him crazy. His name was Billy Joel.”

Debbie also draws inspiration from another pop pianist, Elton John, as well as teen heartthrob George Michael. She also credits Madonna with brave pioneering. “I like her, she’s not afraid of anything. She does what she wants.”

Since Debbie’s music training began at age 5 (she was a member of the Metropolitan Opera Children’s Chorus), she has written and copyrighted about 200 of her compositions. Coming up with enough material for her next album should be no problem. “Yeah, I’ve written tons of songs, tons of ’em. The ideas just come to me. I already have eight tracks down on the new album; we’ll finish it when I get home in October.”

To tide over her fans until then, Atlantic will release Staying Together, the fifth and final single from Out of The Blue. In the meantime, Debbie will be busy on the road, touring in her bus from town to town. “I like it so far. The hotels have been great, too. Nothing fancy. All I really need is a swimming pool, maybe a gym and MTV.”