In the early 1980s, the Louisiana legislature passed a law titled the "Balanced Treatment for Creation-Science and Evolution-Science in Public School Instruction Act."
The Act did not require teaching either creationism or evolution, but did require that when one theory was taught, the other theory had to be taught as well.
Creationists had lobbied aggressively for the law.
Opponents argued that the Act violated the First Amendment's Establishment Clause, which prohibits the government from officially endorsing a religious belief. (See Separation of church and state.)
The State argued that the Act was about academic freedom for teachers.
Lower courts ruled that the State's actual purpose was to promote the religious doctrine of scientific creationism (known also as creation science).
On June 19, 1987 the Supreme Court, in a majority opinion written by Justice William J. Brennan, ruled that the Act constituted an unconstitutional infringement on the Establishment Clause of the First Amendment, based on the Lemon test.Background