His classmates were allowed to wear duct tape over their mouths in silent support of gay rights, but a Wolcott High School student was told he had to remove an anti-gay T-shirt, according to his father.

The T-shirt featured a rainbow with a slash through it on one side, and a male and female stick figure holding hands on the other side with the words “Excessive Speech Day” on the other side.

The student, Seth Groody, wore the T-shirt on April 20 to “express his dislike for gay marriage and his opposition to the perceived message that was promulgated by the school,” said ACLU Legal Director Sandra Staub. The day he wore the T-shirt was a “Day of Silence” intended to bring awareness to bullying and promote tolerance of gay, lesbian, bisexual, and transgendered people.

In a phone interview Tuesday, Edward M. Groody III, Seth’s father, said school authorities forced his son to the office, forced him to take off his shirt, and gave him another shirt to wear.

“I’m not going to call them a bunch of bullies,” he said before emphasizing that the school allowed other students to wear duct tape over their mouths that same day. He referred to the school day as “wasted” because student participation was physically limited by the tape.

But Groody said he doesn’t plan to file a lawsuit at this point.

The ACLU of Connecticut has stepped in to defend Groody by writing this letter to Principal Joseph Monroe.

In the letter, Staub reminded Monroe that asking Groody to remove his T-shirt was a violation of his First Amendment rights.

“The First Amendment was written to protect unpopular speech, which is naturally the kind of speech that will always need protection,” Staub said. “The ACLU has fought hard for same-sex marriage and we couldn’t agree with Seth less on that issue, but he is absolutely correct about his right to express his opinion.”

But the ACLU wasn’t threatening legal action against the school. It was simply writing to remind school officials of long-established laws governing free speech in schools, the legal precedent for which was set by the U.S. Supreme Court in 1969 with its decision in Tinker v. Des Moines, which involved students wearing armbands to protest the Vietnam War. The “Tinker Test” is still applied to similar cases today.

The U.S. 7th Circuit Court of Appeals also found in favor of the students in 2011 in a relevant decision involving high school students who opposed the Day of Silence event and wore shirts that read “My Day of Silence, Straight Alliance” on the front and “Be Happy, Not Gay” on the back.

A staff person who answered the phone in Monroe’s office Tuesday declined to comment.