Dozens of students protested at an Edmonton Catholic high school Tuesday after being told to remove decorations marking the city-wide pride celebrations that kicked off in Edmonton this week.

As a handful of students used pressure washers to erase a large rainbow flag etched in chalk on the ground at the entrance to Blessed Oscar Romero High School, their numbers grew and morphed into a protest.

More than 30 students refused to return to class.

"This is everybody showing our pride," said one student, as a staff member urged them to go back inside.

The controversy began a day earlier when student council members hoisted a rainbow flag inside the school and wrapped four pillars in rainbow colours.

On Tuesday morning, student president-elect Francis Nievera was called into the principal's office. He said he was told all the decorations must come down because the chalk was being tracked inside, which he said was understandable. But those weren't the only reasons.

Student union president-elect Francis Nievera suggested students protest to show their support for pride celebrations. (Trevor Wilson/CBC News) "They said putting up flags was a political statement and it made some people uncomfortable and we need to make everyone feel comfortable," said Nievera, an openly transsexual and transgender Grade 10 student. "To have it all torn down in less than a day kind of sucked."

He said as far as he knew, the decorations had been authorized by the school.

Prior to the protest, a video shows an emotional Nievera, near a handful of supporters including the school mascot, address students from the stage in the school cafeteria.

"We have to take down all the decorations today," he said, setting off boos from the crowd. "But I just want to say because of this I really don't feel safe."

Oscar Romero students refused to return to class after being told to remove pride decorations. (Jenya Sergeeva) "If you guys want to help support pride week, even though all of this will be taken down, feel free to come outside and protest," he suggested.

Among the crowd was Grade 12 student Kennedy Harper, a member of the pride committee.

"It seems like along with the chalk they were just washing away their identity," said Harper, explaining the decorations were important because of the strong LGBTQ community at Oscar Romero, where students also have a gay-straight alliance.

'It was really nice to see everyone come together in the face of injustice. - Kennedy Harper, Grade 12 student

But Harper also saw a bright spot in Tuesday's events.

"It felt really good for a little while, seeing the school really come together and standing up for the rights of minorities whether they're part of the LGBTQ community or not," said Harper, one of several students who said they were told their actions could get them suspended.

"It was really nice to see everyone come together in the face of injustice."

Decorations not authorized: board

A spokesperson with the Edmonton Catholic school board confirmed the principal told students to remove the decorations and called them a political statement. She said the decorations were not authorized by the school.

"Of course anything unauthorized would come down," said Lori Nagy, adding students weren't told they would be suspended and the principal had also offered to work with students on other pride celebration activities.

The administration said chalk was being tracked inside. (Monica Gugliotta) By Tuesday afternoon, however, Nagy said the administration had partially reversed its decision, making the concession that the "flags will stay up this week."

But it appears that message never reached the students, who finished scrubbing away the chalk and ripping down the flags after school. They only learned about the reversal from CBC News afterwards.

Students removed the pride flag from the entrance of Oscar Romero Tuesday. (Christina Crowell) "Dang, I wish he'd told us," Nievera said in a text message.

andrea.huncar@cbc.ca @andreahuncar