A school district that was sued for holding a prayer rally at a school assembly and prayers at official events has agreed to end its promotion of religion. A federal judge on Thursday made final a consent decree in which the Chesterfield County schools admitted to violating the separation of church and state. Under the decree, school officials may not encourage prayers at events or allow endorsement of religion in the classroom. The suit was brought by the American Civil Liberties Union on behalf of a middle-school student who objected to the evangelical assembly and other Christian activities at school.