UPDATED 05/11/11 8:33 a.m.

NAPERVILLE, Ill. (CBS) — When the classic movie “Fight Club” came out in 1999, the oldest of today’s middle school students were toddlers, and the youngest hadn’t been born yet at all.

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But that didn’t stop a group of boys, ages 11 to 13, from starting their own fight club at Jefferson School in Naperville – a choice that attracted the attention of police.

Police said the investigation started in March when a police officer assigned to the school noticed a boy leaving the locker room with a black eye one morning.

Police learned that eight or nine boys were meeting in the locker room and conducting voluntary fights modeled after the movie “Fight Club,” which starred Brad Pitt, or televised mixed martial arts bouts.

The boys were having the fights in the locker room, which was open so that students could get ready for first-period gym, and at some of the boy’s homes, District 203 spokeswoman Susan Rice said. One of them was videotaping the fights on a cell phone, she added.

The group had rules about not hitting in the face, as well as code words, and some of its videos had been uploaded to YouTube.

Rice said the boys involved were disciplined but would not say what penalties they faced, citing confidentiality rules. She said such punishments range from detention to expulsion, though in this case they “fell somewhere toward the middle.”

The school no longer leaves the locker room open before first-period gym, Rice said.

In an unrelated case Friday at Naperville North High School, police found a student carrying a video camera that featured him and another teen talking about making a “fight club”-type video with no blows allowed to the face.

“I guess they wanted to be legends on YouTube,” police Sgt. Russell Wolf said.

The Sun-Times Media WIre contributed to this report.