BOSTON -- A Billerica, Mass., mother is furious after her 14-year-old daughter was suspended for a day from her middle school for wearing a T-shirt that said "SOPHOMORE 69."

Christina Morrison, an eighth-grader at the Marshall Middle School, was sent to the office Tuesday when she arrived at school wearing the shirt. The assistant principal told Morrison and her stepfather that the shirt was "sexually explicit," and that she was being suspended for the day, the Lowell Sun reported.

The teen said she felt like crying because she only wore the shirt she'd recently purchased from a store called Urban Behavior because she liked it.

The school principal, Roland Boucher, said he wouldn't talk about the specific incident, but added that the school's dress code prohibits "any clothing that displays offensive language or images or suggests inappropriate or illegal behavior is not allowed in school."

An attorney for the American Civil Liberties Union of Massachusetts said she believes such a dress-code clause would violate the state's Student Free Expression Act, which "protects even speech that could be considered 'vulgar, lewd or offensive' as long as it is not disruptive."

Morrison's mother, Kimberly Cifelli, said the school should apologize to her daughter and wants the suspension expunged from Morrison's record. She said she cannot imagine how the school can say the shirt is sexually explicit.