Prosecutors in Westchester County, N.Y., have agreed to reduce the charge filed against a group of teenagers accused of affixing alarm clocks to the walls of their high school as a senior-class prank. Eight of the 19 students from the Hendrick Hudson High School in Montrose, a middle-class suburb about 45 miles north of Midtown Manhattan, have accepted the offer; the others are expected to do the same when they appear in court over the next two weeks. The original charge, of placing a false bomb, is a felony that carries a maximum prison sentence of 16 months to four years. The reduced charge, of attempting to place a false bomb, is a misdemeanor with a maximum penalty of one year in jail. The misdemeanor charge will be expunged from the students’ criminal records if they stay out of trouble for six months, attend one counseling session and perform 25 hours of community service.