Ever wonder as an adult what it would be like to be in high school and possess the knowledge and wisdom you now have?

Ever wonder whether the discipline forged through years of adult responsibility would have taken you to the head of your class? Whether your growth into a wiser, more secure individual would guarantee the social success that eluded you the first time around?

Author Todd Gallagher, 33, tested that theory by enrolling for a semester of classes at Trinity Christian School in Forest Hills in August.

He also is working on a book, film and potential television pilot about the experience.

A Delaware native, Mr. Gallagher was a National Merit Scholar as a teenager. But he was expelled from two private schools, St. Andrew's School in Middletown, Del., and Shady Side Academy in Fox Chapel.

He enrolled at Greensburg Central Catholic High School in 1994, and graduated the next year with a 1.7 grade point average.

Fourteen years later, convinced that he had matured and hoping to redeem himself for past underachievements, Mr. Gallagher abandoned life in Los Angeles for his parents' home in Shadyside and headed back to classes in August.

His verdict after a single semester: You may do better, but it's not half as easy as you think.

"I would say to people, if you got a 2.0 in high school, unless you really make an effort to change, you're going to get a 2.0 again," said Mr. Gallagher, a former ESPN writer.

"Which is what I would have gotten, except once I got in there and struggled, I did change.

"The kids who are getting 4.0s are really smart kids, they work really hard, pay attention in class and do all the things they're supposed to do.

"If you didn't do that when you were in high school, what makes you think as an adult you're necessarily just going to?

"Everyone says I would do great, but unless you've changed something about [yourself], you wouldn't. You would do just as bad."

Trinity headmaster Dale McLane said the project was approved after strict guidelines were established during more than a year of meetings with Mr. Gallagher, students and parents.

There would be tight restrictions on Mr. Gallagher's interactions with students.

Mr. McLane said adults who underestimate the difficulties of high school are probably overestimating their learning abilities.

"As you get older, some things become more difficult," he said. "Anybody coming back would think it would be easy, but it isn't. Our brains don't function the same."

Bodies, apparently, don't either. Mr. Gallagher, a former multisport athlete, initially had dreams of dominating, especially on the soccer field. He ended up serving as equipment manager for the boys' soccer team.

He admits he came short of the goal, but said the experience made him a better athlete than the first time around.

Mr. Gallagher said his mental and emotional maturity - along with 2-mile runs for soccer practice that led to the loss of 40 pounds - gave him the focus and drive to improve.

He said his maturity helped him to keep his cool and to make friends under difficult circumstances. Mr. Gallagher, after all, was twice the age of many students, and realized that many are more relaxed around their peers than adults.

Senior Anthony Marchilena, 17, said Mr. Gallagher related relatively well to students.

"I was expecting a professional guy to be in our class, not to get to talk to him that much," Anthony said. "When he actually came to the school, he was a lot more personable than I imagined."

Trapped between the adolescent and adult worlds, and limited in interactions with classmates, Mr. Gallagher ended up cultivating one of his best friendships with Mr. McLane.

"When you're a kid," Mr. Gallagher said, "you'll talk to your principal sometimes and say, 'What is this person saying? I can't believe this!'

"But as an adult, you hear them differently and try to understand what they're saying. And he's a really logical guy, so it would make sense to me why things would happen, which would make me less upset."

Actually, all parties involved got more than expected from the experience. And there may be a book, film or TV pilot.

Mr. McLane said the school got exposure for providing a supportive environment that welcomed and reformed the former class clown, and that the headmaster gained a true friend.

Anthony said he was rewarded with a senior experience like no other.

"Todd gave a lot back to our school," he said. "He really influenced myself and other people. He used his experience to give advice, and he made my senior year fun, exciting and unique."

After six months and "too many detentions," Mr. Gallagher walked away with a 3.8 GPA, a new set of friends, material for his next project, and a true measure of just how much he has grown since adolescence.

"I was nicer now. This time, I wasn't as angry," he said.

"I was a lot different this time. It wasn't just getting better grades. I'd like to think at least I was a better person."

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