A group of high school girls in Delta, B.C., ran across a football field almost naked during half time of a game last week and sprayed silly string on members of the opposing team. (CBC)

Twelve female high school students sporting only their underwear and duct tape around their breasts ran across a football field during their school team's home game last week in Delta, B.C.

The principal of South Delta Secondary School said Wednesday he doesn't want to see a repeat of the prank and has issued warnings to the Grade 12 students, most of them cheerleaders of the home team.

"We don't take it lightly. This is a school. [In] schools, we hold higher ideals than we do in, say, the mall," Ted Johnson told CBC News in an interview.

The streaking happened on Oct. 28 during a Delta Sun Devils game against the Lord Tweedsmuir Panthers of Lord Tweedsmuir Secondary School from Surrey.

South Delta Secondary School principal Ted Johnson says the girls who streaked at the game will be suspended if they do anything else wrong. (CBC)

Video footage obtained by CBC News shows a dozen South Delta students wearing very little run across the field and spray silly string on the opposing team during half time.

Johnson said he warned students last month not to streak at this year's final game of the season but was, obviously, ignored. Many parents and children left the game in disgust after the prank, he said.

"Our position is one that we don't celebrate this. We don't find it funny," he said.

The girls, calling what they did a "harmless prank," said streaking is a tradition at their school.

"It's just kind of like a fun [graduation] prank for our year, and it's been going on for a couple of years now," said one of the girls, who wanted to be identified only as Rochelle. "It was pretty much out of fun."

"They [school officials] just need to lighten up, really. It was a joke," Michelle, another girl, said. "When our parents were in school, … there were way worse things, so this isn't a big deal really."

Johnson said he has told the girls involved that they will be suspended from school if they do anything else wrong.

They must also encourage younger students to end the streaking tradition, Johnson said.