Three eighth-graders from northwest Indiana who say they were expelled after joking on Facebook about which of their classmates they would like to kill asked a federal judge Wednesday to order the district to allow them to return to school.

The American Civil Liberties Union of Indiana filed a lawsuit on behalf of the three 14-year-old girls in federal court in Hammond, claiming that Griffith Public Schools violated the students' free-speech rights.

The girls were suspended and later expelled in January for the remainder of the school year after a classmate's mother alerted officials at Griffith Middle School to the girls' Facebook posts, the lawsuit says. The suit says school officials told the girls they had violated school policy against bullying, harassment and intimidation.

School officials didn't immediately return a phone call seeking comment Wednesday.

ACLU attorney Gavin Rose said it was clear the girls were joking because their remarks were accompanied by smiley faces and other emoticons, along with Internet abbreviations for laughter, such as LOL.

"The fact of the matter is that no reasonable person looking at this conversation would think that these girls were going to go out and inflict harm on anyone," Rose told The Associated Press. "If you make a legitimate threat against someone ... you don't follow it up with an emoticon."

The posts were made after school on the girls' personal electronic devices, not on school computers, the lawsuit says, and were visible only to the girls' online friends who were allowed access.

"Schools do not possess infinite reach into the private lives of their students," Rose said in a separate statement.

Since 1969, the U.S. Supreme Court has generally ruled that students have free-speech rights, and schools can prohibit their speech only if it is vulgar or disruptive to schoolwork or other people. The lawsuit claims the posts did not cause any disruption at school, and no one at school mentioned the posts the following day.

The district told the girls they would be permitted to proceed to ninth grade at Griffith High School this fall, the lawsuit says, but only one of the girls intends to attend that school.