If you prefer Pepsi over Coke, you’re frequently out of luck on the Iowa State campus.

But at least you won’t be suspended.

Mike Cameron, a senior at Greenbrier High School in Evans, Ga., was suspended for one day after wearing a Pepsi T-shirt during a Coca-cola promotion at the school.

Cameron wore a shirt brandishing the Pepsi logo underneath another shirt until just before a group picture in which students spelled out “Coke.” Right before the cameras clicked, Cameron took off the overshirt and landed himself a suspension.

Ridiculous? Absolutely.

Schools have the authority to prohibit some clothing, including vulgar and obscene T-shirts. But schools have absolutely no business telling their students what brand-name T-shirts can and cannot be worn, even on a promotional day.

School principal Gloria Hamilton defended her harsh action by saying, “These students knew we had guests,” referring to Coke’s regional president and other company speakers.

Sure, the school had “guests.” But since when do guests to a school mandate the specific brand of T-shirt a student wears?

The Coca-Cola officials were at the school for a Coke in Education Day, which was an effort by the school to win a local contest which offers $500 to the school to distribute promotional discount cards in the most creative way. The school was also vying for a $10,000 national prize.

The high school also had chemistry students test the sugar content in a can of Coke, and home economics students baked a Coke cake.

Hamilton said Cameron’s prank was “disruptive and rude,” and compared it to “obscene gestures” that some students make during school pictures, a crime that also carries a suspension.

But Cameron’s refusal to go along with corporate sponsorship was merely an exercise in free speech, something a school should never condemn.

Interestingly, Coke officials didn’t even notice Cameron’s exercise in free speech, and it didn’t bother them when they found out.

But Greenbrier did attract the notice of the Pepsi Corporation. Spokesman Brad Shaw said Cameron had “impeccable taste,” and promised to outfit him in “plenty of Pepsi shirts.”