Final answer:
The Supreme Court uses the Lemon Test in establishment cases to ensure laws have a secular purpose, do not advance or inhibit religion, and avoid excessive government entanglement with religion.
Step-by-step explanation:
The common standard the Supreme Court uses in establishment cases is known as the Lemon Test, a three-part test created to determine when government involvement with religion becomes an unconstitutional 'establishment.' For a law to pass the Lemon Test, it must satisfy three criteria. Firstly, it must have a secular legislative purpose; in other words, its main objective should not be promoting or demoting religious practices. Secondly, the law's primary effect must be one that neither advances nor inhibits religion, ensuring neutrality in matters of faith. Lastly, the law must avoid any excessive government entanglement with religion, which would imply undue influence or control over religious affairs by the state. The application of this test is a crucial aspect of how the Supreme Court has interpreted the Establishment Clause of the First Amendment.