The discovery at the Ricardo Flores Magon Academy in Adams County came as students had been learning about bullying.
Back to the smart board?
Officials say the post-school brawling was a loosely organized club.
"Fight clubs, they are calling them fight clubs," school board chairman Virginia Longoria said. "Kids are getting together and daring each other to fight each other."
"They all admitted to planning it. Some of them admitted to actually physically fighting," interim head of the Academy Marcelino Casias said.
CBS Denver reported some were given in-school suspension for the fighting that took place in bathrooms, and mainly involved 5th and 6th graders.
"Our kids understand that it is not going to be tolerated, and it is not good and violence is not going to be something that we support," Longoria said.
"Actually they have been taking bullying classes for the last two weeks," Casias said. "We take it very seriously."
While the school insists no one was hurt parents told CBS Denver children came home with cuts, bruises, and scrapes from the fighting.