We think that, by using its public school system to encourage recitation of the Regents' prayer, the State of New York has adopted a practice wholly inconsistent with the Establishment Clause. There can, of course, be no doubt that New York's program of daily classroom invocation of God's blessings as prescribed in the Regents' prayer is a religious activity. According to this passage, the main reason the Supreme Court ruled the prayer unconstitutional was because

time was taken away to recite the prayer.
the state was promoting religious activity.
religion was against the law in New York
the prayer promoted Catholicism.