Sitting in the auditorium of the Trinity School on a cold night, a few parental gasps could be heard as children talked about mounting SAT pressure and fielded questions from parents about oral sex.

Granted, this is not the usual sort of banter one expects from a gathering co-hosted by the Parents League of New York, a 93-year-old blue-blood institution considered the gatekeeper between parents and the city’s private school admissions officers.

But this was Teen Scene, an annual gathering in its 20th year where parents of private school students come to learn about what their teenagers are up to when they are up to no good.

Last Monday night, about 600 parents packed into the pews at Trinity on the Upper West Side, sitting in rows with copies of hymns tucked into the pews ahead of them. One mother crouched on the floor with a fur coat draped across her lap while another clutched her Louis Vuitton purse from her perch on the blue carpet.

Fifteen teenagers invited to speak on behalf of their peers sat behind folding tables on the stage. They represented a cross-section of the city’s finest private schools.

One senior had just been accepted to Harvard, another to Brown. Some played for the fencing and lacrosse teams, while others spent their summers interning for investment banking firms and mortgage and loan companies. None was older than 18.

“They’re impressive,” beamed the moderator, Lucy Martin Gianino, a middle-aged woman with a tough-love attitude who helped start the event two decades ago for a group called Parents in Action.

The group formed in 1986 after a senior from Spence was killed in a hit-and-run accident while coming out of a Manhattan bar late one night. It was a wake up call for many well-to-do parents that their children were not immune to the dangers associated with drugs and alcohol abuse.

“Are teenagers using dental dams and condoms when they have oral sex?” one parent in the middle of the room stood up to ask.

A senior boy wearing blue-and-white boat shoes and a sweater with the collar up took the microphone.

“I’d say that the male mentality on that is that oral sex with a condom is akin to going out on a sunny day with a rain coat,” he said.

Some audience members laughed, others gasped.

They talked about homework, sex, drugs, clubs, and something even more terrifying to many parents – the Internet.

After 20 years, there’s not much Ms. Martin Gianino hasn’t heard, and before opening the floor to the star attraction – the teenagers – she reminded parents to think of their own youth.

“If we’re able, reach back into your own teen years to remember the choices that we made, the risks that we took, the bliss that we felt even as we are caught up in the intensity of the complex choices facing our youngsters today,” Ms. Martin Gianino, who works as an actress and real estate agent, said.

For many students – whose parents will have invested almost a quarter million dollars in their education before they even get to college – there is an immense amount of pressure to succeed.

They deal with it in a variety of ways ranging from sports to drinking.

“I know three kids who don’t drink, and one of them it’s because of health problems,” one panelist explained.

Teen clubs?

The youngsters do frequent the cluster of burgeoning clubs just for teens, at which no alcohol is served. But they get drunk first. Who wants to be limited to the $8 bottles of Red Bull and Vitamin Water?

Cocaine is “girlie.” Sorting crushed up prescription pills like Ritalin and Adderall is tougher, more rebellious. Some buy their friend’s attention deficit disorder medication and take them the old fashioned way, with a glass of water, to help with homework or concentration for a test.

Most teenagers aren’t promiscuous when it comes to sex, they said, but oral sex “isn’t really considered sex,” as one teenager pointed out.

One senior with long blond hair emphasized the importance of communicating with children about sex and explained that her mother takes her to get birth control. “That’s just the kind of relationship that we have,” she said.

In order to deal with parents’ post-traumatic stress disorder, the organizers have added a new follow-up event this year – “Aftershock.” On Thursday, parents are invited to Temple Israel for a forum to discuss the issues they encountered at Teen Scene.

At the end of last week’s event parents were asked to pass in cards with questions about they had learned. One parent scribbled, “Where do they get alcohol?”

On the way to the subway station after the event, two mothers shook their heads in disbelief.

“It’s not surprising what they said, it’s just surprising that they said it,” one mother said. “I mean, there was a room full of parents there.”