INDIANAPOLIS (AP) — The American Civil Liberties Union is suing a northwest Indiana school district that it says expelled three eighth-graders for joking on Facebook about which of their classmates they would like to kill.The lawsuit filed Wednesday in federal court in Hammond alleges Griffith Public Schools violated the three 14-year-old girls' free speech rights.The girls were suspended and later expelled in January after a classmate's mother alerted school officials to the Facebook posts. The suit says school officials told the girls they had violated school policy against bullying, harassment and intimidation.ACLU attorney Gavin Rose says it was clear the girls were joking because their remarks were accompanied by smiley faces and other emoticons.School officials didn't immediately return a phone call seeking comment.