In wallace v. jaffree the supreme court struck down an alabama law that required one minute of silence for prayer or meditation in all public school classrooms because

It violated the first amendment. The first amendment guarantees the right to freedom of religion. Within this freedom of religion there is an idea called the establishment clause. This prevents federal or state governments from establishing an official religion or forcing individuals to participate in religious events. When this case went to the Supreme Court, it was ruled in a 6-3 favor that this violated the constitution, as the school is a public institution that represents the state.