For Kaitlyn Juvik, it was her lack of bra.
A student at Helena High School in Helena, Montana, Juvik was given two options: Cover up or put on a bra because "someone in the building" was uncomfortable.
Here's how she looked:
"You definitely can't tell I'm not wearing a bra unless you're looking VERY hard," she wrote on her Facebook page.
Juvik along with fellow students staged a silent protest and started a "No Bra, No Problem" Facebook page.
Here they are in action:
"I'm not going to check students' undergarments," the school's principal, Steve Thennis, said to MTN News. "We are going to ask them to dress appropriately and if we feel it is inappropriate, male or female, we are going to ask them to cover up."
The big Q: Should unsupported breasts in their natural state under a black top be considered "inappropriate"?
No. At least according to Juvik, who shared this epic meme on her Facebook page after the incident.
It perfectly sums up why she should be allowed to have a choice to cover up or not.
"Different things empower different women, and it's not your place to tell her which one it is."
Correction: June 6, 2016
A previous version of this story misidentified the location of the school Kaitlyn Juvik attends. The school is in Montana.
Correction: June 16, 2016
A previous version of this story included a photo of a different Helena High School than the one Kaitlyn Juvik attends. The photo has been removed. Additionally, this story originally misattributed photos from the MTN News report. The attributions have been corrected.