An Everett school has banned all sports attire that is not Seattle-based over concerns of gang affiliations with certain teams.

Mariner High School Principal Brent Kline explained to the ban to parents, according to MyEverettNews.com.

“Over the past months there has been an increase in gang activity in our Mariner community,” Kline wrote. “We are vigilant about keeping this specific behavior out of our school. We have been successful in the past due to continuing coordination with the Everett area gang task force. Our ever-changing dress code is in response to the on-going learning that we acquire from our partnership with the task force.”

“We made the decision to ban professional sports team apparel as we have learned that gangs are using it as a way to identify themselves. We want our students’ focus to be on school and we want our teachers’ and administrators’ time to be used on teaching and learning — not dress and gang issues.”

Kline also notes that the ban’s wording should have been more specific and that all local colleges and universities will be allowed.

Gangs co-opting sports teams’ apparel for their own use is nothing new, as 710 ESPN Seattle’s Danny O’Neil told Seattle’s Morning News .

“It started in the late ’80s,” O’Neil said. “You saw street gangs begin to use professional teams, most often because of their color combinations, as ways to represent their gang.”

“It’s unfortunate, but I also feel that for school officials, their primary objective is to keep kids safe,” he said.

O’Neil said that it’s not just local gangs and groups that adopt a team’s colors. National gangs have been known to affiliate with teams and their colors.

“You had blue, that was associated with the Crips, and red was associated with the Bloods,” he said. “(But) it could be as simple as a group and how things work with them. It’s not always some overarching, national gang organization.”

Mariner High School was flooded with parents’ concerns over the new ban, which prompted Kline to write the letter.