In response to a National Day of Silence event in April 2006, Zamecnik wore a shirt to school that read "MY DAY OF SILENCE, STRAIGHT ALLIANCE" on the front and "BE HAPPY, NOT GAY" on the back, according to the suit filed Wednesday.
On the Day of Silence, students can refrain from speaking as an effort to highlight discrimination against homosexuals.
According to the suit, one school administrator ordered Zamecnik to remove the T-shirt and another official ordered her to cross out "NOT GAY" with a marker.
The suit alleges Zamecnik suffered unlawful discrimination and humiliation because school officials didn't agree with her viewpoint.
Calls to the Indian Prairie School District and Neuqua Valley High School were not immediately returned Thursday morning.
The Arizona-based Alliance Defense Fund, a conservative Christian litigation group, is representing Zamecnik. Gary McCaleb, senior counsel for the group, said the organization has filed at least eight similar lawsuits nationwide.
McCaleb said the Alliance Defense Fund is trying to "enable Christian students to express a contrasting viewpoint on homosexuality."
McCaleb said Zamecnik and her parents discussed the incident with school officials to work out an agreement allowing the teen to wear a similar T-shirt during next month's Day of Silence event.
The suit said school officials declined the request.