We’re not talking about your mother’s sock hop.

At the 21st century prom, not even the corsage is sacred. That baby’s breath, it turns out, may actually be a cover for contraband.

A stick of gum can be used to smuggle in liquid ecstasy. Buried deep within a tube of chapstick, any number of pills can slip undetected past chaperones.

That’s why, as teenagers become ever more resourceful, local schools are cracking down at dances on everything from chapstick to mouthwash, from deodorant to gum.

“It just seems like for us it’s harder to catch because a lot of times it’s more hidden,” said Vintage High Dean of Students Sharon Anderson, who is preparing for this weekend’s Vintage High Prom.

When students arrive at the Design Galleria in San Francisco, they will be patted down, their bags searched. Chaperones will rummage through corsages and boutonnieres for any illegal substance.

In the event that a student displays unusual behavior, or if any hint of alcohol is detected, chaperones will have a breathalyzer near.

Adhering to a strict zero-tolerance policy, Anderson said chaperones will leave no stone  unturned — or stoner, as the case may be.

That means no liquids whatsoever — no perfume, mouthwash, eye drops.

No mints or gum. No over-the-counter meds.

Prescription medication such as inhalers or birth control pills must be checked at the front and administered only under the supervision of a chaperone.

Even deodorant must be left at the door, said Anderson, explaining the process whereby students roll up and remove the deodorant from its casing, hiding anything from a handful of pills to marijuana in the tube, and then roll the deodorant down.

The stricter-than-ever rules, she said, are an indication of the times. Drug use among teens is more prevalent than it was even during her days as a student in the rebellious 1960s, said Anderson.

And it’s not just Vintage. Schools across the county are upping their precautions in preparation for the prom.

Lipstick traces

At Napa High’s prom last month, the school adopted a controversial chapstick ban.

Just like deodorant, drugs can be hidden in the tube beneath the chapstick, said Anderson, who has also enforced the rule at Vintage in the past.

While interpretations of the rule vary among administrators, some students at Napa High said they were asked to apply their last coat of lipstick before entering the prom.

“Girls were pinching their lips in line before pictures,” said Napa High sophomore Olivia Barker. Others stuffed lipstick into their bras, slipping into the bathroom for a surreptitious application.

Both Anderson and Napa High Dean of Students Al Bahn said their schools will consider permanently implementing the “no lipstick” rule next year.

“Students are very creative,” said Barbara Franco, Napa High principal, earlier this year. “We want to have safe events. … When information comes to us through a reliable source, then we respond to that.”

Students including Mary-Kathryn Peck at Napa High call the policy “obscene.”

“It’s kind of stupid that we have to be forced to dance without chapstick because someone once used it to hide drugs,” said Barker.

“They kind of went over the top,” said Brian Perry, a senior at Napa High.

Anderson defends the rules, however, explaining that parents entrust her with the safety of their children.

“I hold a tight ship, and I would much rather have people blame me for being too strict than not strict enough,” she said.

Some smaller schools rely primarily on their familiarity with students to recognize unusual behavior.

Monica Tipton, principal at New Technology High School, said the school forbids liquids and medications, “but we don’t search handbags or anything as they come in.”

“We could, if we felt there was a need to,” she added. “It’s not that we turn a blind eye to those things. It’s that kids know we are watching.”

At Justin-Siena High School, Dean of Students Steve Meyer said chaperones don’t ban meds, but keep an eye out for unusual behavior. He also keeps a breathalyzer handy, and is trained to conduct a sobriety test.

Though he insists he trusts his students, Bob Yeend, Justin-Siena junior class moderator, acknowledged, “If a student really wanted to bring some unauthorized substance, I suppose they could.”

Despite the admitted need for increased vigilance, school officials said students typically behave, given the threat of not being able to walk the stage at graduation.

Additional precautions — such as scheduling school meetings before the prom, having a deluge of chaperones and enforcing a policy that prohibits students from leaving prom early — keep the majority of students in line, according to administrators.

‘Freak’ out

Additional rules extend all the way from dress to the type of dance allowed.

A sign above Napa High’s Activities Office depicts two wriggling stick figures. The sign declares, “No freaking.”

The policy, implemented at local schools across the county, refers to a particularly raunchy style of dance. Vintage High Activities Director Gail Sims describes freaking as a modern style of “bump and grind.”

“I don’t think our parents’ generation would even be able to make it at today’s dances,” Barker said with a laugh. “My mom doesn’t even know what freaking is.”

At her prom, one student danced with the sign itself, said Barker. Upside down, the stick figures demonstrated an especially vulgar pose.

“We say no freaking, and we try to enforce it,” said Sims, “but it’s a crazy bunch of kids, and when you get 600-plus students out there enjoying the dance, all we can do is do our best to make it appropriate.”

“We’re not prudes,” added Sims, “and we understand that each generation has their own style of pop dancing. We just don’t want it too sexual on the dance floor.”

Meyer said at Justin-Siena, chaperones “walk around and try to keep them as separated as they can.”

Chaperones at prom must also screen for inappropriate attire, said Sims.

Young men should wear tuxedos, she said, though suits are acceptable as well.

No zoot suits, as chains are not allowed.

“They must remain fully clothed,” added Sims. “Young men can only take off their jackets.”

Ladies’ formalwear must also be appropriate, she said, and dresses may not be lifted above the waist.

In language students might understand, Sims explained: Dresses similar to those worn at the Oscars are acceptable. Those worn at the MTV Awards are not. The Grammies are a gray area, she said, noting that this year’s Grammies were more tasteful than most.

Meyer said with a sigh, “I think through the years things have definitely changed. … Every adult should go to a high school dance and experience it and see what today’s society is like. It might help them understand teenagers a little better.”