If Greeley-Evans School District 6 students want to wear a Cam Newton jersey on their last day of class before the Super Bowl, it’s all good.

But they better not let administrators catch them wearing a Peyton Manning jersey today.

Since 2011, the District 6 universal dress code has outlawed the number 18 as it appears on clothing, including jerseys. Students also are barred from displaying the numbers 13, 14, 31, 41 and 81. It all comes back to gangs. The Denver Broncos’ run to the Super Bowl won’t yield any exceptions.

“Gangs use those items of clothing for a few reasons,” District 6 spokeswoman Theresa Myers said. “They use them to recruit and they use them to intimidate.”

Myers said there is very real risk associated with displaying the banned numbers, especially for students who aren’t part of a gang associated with the numbers, such as the 18th Street Gang.

The policy was created in 2011, but it wasn’t met with a lot of push-back until Peyton Manning signed with the Broncos the next year. But today, even with the Broncos’ run to the Super Bowl and all of the “Broncos Days” at local schools, Myers said district officials haven’t really heard complaints.

“I think as time has gone on, it’s just an expectation,” Myers said. “Now, people are just like, ‘That’s the rule.’ ” The rule doesn’t apply only to Broncos gear. Any sports-related jerseys with the numbers, with the exception of student’s school teams, are banned. Even generic T-shirts can’t contain the controversial numbers.

So, no Odell Beckam No. 13 jerseys, no Dirk Nowitzki No. 41 and no Max Scherzer No. 31 jerseys are allowed.

John Gates, District 6 director of safety and security, helped develop the policy. As a former cop, Gates was aware of the gang-related symbols. In seeking a way to combat the issue in schools, Gates met with counterparts in other school districts, and he found some have had success in curbing gang activity by implementing dress codes such as the one in Greeley, Myers said.

It’s not just numbers. The District 6 dress code bans gang-related tattoos, shaved or notched eyebrows, red or blue shoelaces or shirts and bandanas, among a host of other things.

These items can be recruiting tools, Myers said. If a student is interested in gangs, they would know who to approach if the code wasn’t in place, for example. Or, and this still happens today, Myers said, students may pull a bandana out of their pocket to tell other gang members who they are.

Although there’s some indication gang-related activity has gone down in Greeley generally, students shouldn’t expect to trot out their Manning jerseys anytime soon.

“Not right now; not in the foreseeable future,” Myers said. “Gang activity is still a reality here. There’s no sign that it’s going to go away completely, and until it does, we will probably have some kind of dress code in place to protect our kids in school.”

Tyler Silvy covers education for The Greeley Tribune. Reach him at tsilvy@greeleytribune.com. Connect with him at Facebook.com/TylerSilvy or @TylerSilvy on Twitter.