Jan. 10, 2008  -- More than a dozen Eden Prairie, Minn., high schoolers walked out of class to protest the school's punishment of students caught by administrators partying on Facebook pages.

The move came after 42 students at the well-regarded Minnesota public school were questioned by school administrators who viewed online photos of the young people drinking alcohol.

"Photos were presented to us of some of our students in possession of, or consuming, illegal substances," said Principal Conn McCartan in a written statement provided to ABCNEWS.com.

Thirteen of the 42 students involved in the investigation have since been punished, according to McCartan.

"All students who participate in school activities have to sign a liability brochure saying they understand the rules and will follow them," said Dave Stead, the executive director of the Minnesota State High School League, of which Eden Prairie High is a member. "Rules include not using, possessing, giving, buying alcohol or drugs. These students signed the pledge and then violated it — so appropriate penalties were given."

The majority of high schools in Minnesota collaborate to determine punishments for such incidents, Stead told ABCNEWS.com, and Eden Prairie has since abided by them.

For the first offense of breaking the pledge, students are suspended from two extracurricular events or are suspended for two weeks, whichever punishment is greater, Stead said. With each additional offense, the length of the suspension increases, rising to 28 days or 16 events.

"We hope that the punishments will be a deterrent, but also hope that the students will learn how important it is to sign contracts," said Stead, who added that this sort of incident has occurred at other schools in the state, but he thinks Eden Prairie's good reputation has likely added fuel to the fire. "They must learn there are some things you can and cannot do."

How, exactly, the school administrators obtained the photos is unclear — many students' profiles were "limited" and therefore could only be viewed by people they accepted as friends on Facebook.

Stead said that he believed the photos were presented to the school administration, and McCartan has denied allegations that the school sought out the photos.

Michael O'Leary, whose son is a sophomore at Eden Prairie but was not involved in this incident, is upset about how much negative attention the school is getting.

"I don't think [Eden Prairie] is any different from any other school," said O'Leary, who added that he does speak to his son and friends about the dangers of underage drinking. "No matter where you go you'll have this type of problem, but it doesn't need to be publicized."

The school's outstanding reputation as one of the best schools both academically and athletically — the football team has won several state championships in recent years —is more important that its drinking culture, said O'Leary.

"They're good kids who are smart kids," said O'Leary. "That's not to say we don't have problems, but we're comparable to other schools."

Max Friedman, one former Eden Prairie student whose sister was involved in the investigation, said that drugs and alcohol were prevalent during his high school years.

"In terms of drinking, the high school is probably the same as any other high school in the United States," Friedman told ABCNEWS.com. "Drinking is always available and marijuana was also used."

His sister Natalie Friedman told the Minnesota Star Tribune that she was questioned because of a photo depicting her behind a bar at a friend's house, surrounded by drinks.

"I didn't get into any trouble," Natalie Friedman told the paper. "It's not going to stop kids from drinking. We're just going to re-evaluate what we put out in public. We're going to be more cautious."

The Associated Press contributed to this report.