The Supreme Court has ruled that states may not mandate the teaching of creationalism. In the view of the Court, states which require their schools to teach creationalism are, in effect, imposing a religious doctrine on them.
In 1925, in the famous Scopes trial, Clarence Darrow defended John Thomas Scopes from charges of having taught evolution, which was outlawed by Tennessee law. Darrow lost, and Scopes was convicted. In 1968, in the case of Epperson v Arkansas, the Supreme Court unanimously reversed a conviction of an Arkansas biology teacher convicted of teaching evolution in violation of an Arkansas statute. In 1981, Louisiana adopted a law that required that creationalism be taught along with evolution in Louisiana schools. In the 1987 decision of Edwards v Aguillard, the Supreme Court ruled that the law was unconstitutional. Since creationalism is a doctrine that embodies the “belief that a supernatural creator was responsible for the creation of mankind,” the requirements that it be taught was, in effect, supporting religion.