Credit: Kristi Davis

Kristi Davis' son started off his year at Wade Hampton High School last week wearing what he thought was just a shirt with a flag on it. But by halfway through the day, he knew otherwise.

"The school resource officer and gang investigator pulled him aside after lunch," Davis said. "First, they asked what gang he was involved in, and he said, of course, no gang, and then they told him not to wear it anymore."

That's because the flag on the tenth-grader's shirt was designed out of red and blue bandanna print, and gangs often display their affiliations using bandannas of different colors, according to police.

"Since both blue and red are colors for known national gangs and these gangs typically use bandannas, he was asked to turn the shirt inside out and he finished the day at school," said Lieutenant Michael Hildebrand of the Greenville County Police.

When Davis' son came home and told her what happened, Davis says she was frustrated the school never educated parents about what counts as gang symbols on clothing. She went back to the school to talk with administrators about the issue.

"While I was in the office that day, I saw about 20 other students with bandanna or paisley print," Davis said. "It's time for the school board to step in."

Wade Hampton High School did not immediately respond to ABC News' call for comment.

Davis said she never would have bought the shirt from American Eagle if she'd known her son couldn't wear it to school. She suggested the district put this type of information in the school handbook or even adopt a stricter dress-code policy.

"If this is such a problem, why don't we wear uniforms?" she said. "Put them in uniforms. I'm fine with it."

Whether the students would be happy with that change is another question.