Not long after the mischief started, Chris Shoemaker says, he knew it was a bad idea. He and his friends were on the brink of graduation at Herndon High School and intrigued by the idea of a senior prank — an annual rite of passage at high schools that can involve shaving cream, paint, water balloons and sometimes worse.

Someone mentioned baby oil. The teenagers imagined their classmates skating across hallways. It sounded comical.

It was not. No one was injured in the escapade, but the slicks of oil that appeared June 6 in several hallways and stairway landings left six senior boys suspended during their final days of school, according to students involved. Three, including Shoemaker, are banned from Thursday graduation ceremonies, the students said.

For some schools, senior pranks can be a yearly headache, with each class trying to leave its mark and high jinks ranging from the harmless to hazardous. Principals often make the call on consequences — weighing the extent of problems caused, with an eye on the difficulty of excluding students from the grand finale of high school.

In Fairfax County, this decision-making comes as the school system is under a discipline microscope, with the School Board continuing to study how students are punished for infractions.

Shoemaker and his family are appealing the graduation ban Wednesday, arguing in part that all six teenagers involved should have been punished equally — without losing graduation privileges. An honor student, Shoemaker, 18, has taken 11 Advanced Placement courses at Herndon, and he played varsity basketball. He said he has never had a discipline infraction.

“I feel I should definitely have been punished, and I definitely did something wrong, and somebody could have gotten hurt,” said the teen, who apologized in person Monday to the principal. He said he would gladly make amends through community service or school cleanup — “anything other than not letting us walk” across the graduation stage, he said.

Some classmates embraced the cause on Twitter, employing the phrase “#LetTheBoysWalk2012.” Herndon students wore T-shirts with those words. The principal ordered the shirts to be removed or turned inside out. Then the American Civil Liberties Union stepped in.

“Punishing students for their political speech teaches a profoundly negative lesson about the school attitude toward the nation’s most cherished freedoms,” the ACLU wrote to Principal William Bates.

Fairfax County officials had no comment on the disciplinary actions, which are considered a private matter, schools spokesman John Torre said. He noted that in the weeks before graduation seniors are reminded of possible consequences of misconduct. Torre said “a number” of students do not attend graduation because of suspensions.

A vexing day

June 6 was clearly a vexing day for Herndon High administrators. It started with the discovery of spray paint on the building. Then there was the baby oil incident. Later, someone pulled a fire alarm.

Shoemaker and another student involved in the baby oil incident said the slicked floors posed a danger for a matter of minutes — perhaps five to 10 — before the students were caught and the affected areas were cordoned off.

Students were held in their classes while the oil was cleaned up, Torre said. It was a day of class and state exams, he said, and the incidents caused a major disruption.

For principals, such cases are a tough call, said Patrick Larkin, a Massachusetts principal who has been honored by the National Association of Secondary School Principals.

“If it’s something that puts somebody at risk or in danger, it’s a fine line,” he said. Unless irreparable harm is done, he said, he looks for consequences apart from graduation ceremonies: community service, for example, or missing a graduation-related party.

Larkin called denying graduation “the nuclear weapon of student discipline.”

In the Washington area, pranks are not uncommon.

River Hill High School in Howard County was spray-painted in May in a senior prank that included toilet-papering trees and moving trash cans into the street. Thirty students were disciplined and tasked with an extensive cleanup before graduation, said spokeswoman Patti Caplan.

They were not excluded from graduation ceremonies. “The principal certainly has the right to deny participation,” she said, but generally school leaders use it as a last resort.

In Herndon, Bob Shoemaker, father of the suspended teen, said he recognizes the danger created by the oil-slick floors and supports punishment. But it seems harsh, he said, to shut down the possibility of attending graduation, after 13 years in school, because of a “13-minute mistake.”

His son said the idea never crossed his mind that he might lose his chance at attending graduation or be suspended.

The teen said he bought baby oil for the prank but then realized the problem when a teacher admonished one of his friends, who was squirting it on the floor.

Shoemaker said he did not spread the oil and walked back to class, where he said he remained only briefly before he was pulled out for questioning.

He said he immediately admitted his involvement.

But Shoemaker said that in his statement to a security officer, he used the word “we,” which he says school officials viewed as an admission that he had actually poured the oil on the floor. A security officer made a note of that impression on Shoemaker’s written statement.

‘Weren’t really thinking’

Ashkan Naderi, 18, who also is set to miss graduation because of the baby oil prank, described the original idea as “a quick, funny, slip-and-slide kind of thing.”

“We weren’t really thinking,” he said. “We were just trying to go out with a senior prank that would be remembered. We definitely didn’t mean for anybody to get hurt.”

On Monday, Naderi said, the principal told his mother that the family should consider collecting the teenager’s cap and gown and taking photos at home.

“All I’m doing,” Naderi said, “is hoping and praying that something . . . changes their decision.”