Why did Lemon v. Kurtzman find state support for religious schools unconstitutional?

In Lemon v. Kurtzman (1971), the U.S. Supreme Court ruled that state funding for nonpublic, religious schools violated the establishment clause of the First Amendment.12

The Court found these statutes unconstitutional primarily because they resulted in an "excessive entanglement between government and religion," which was the third prong of the newly established Lemon test. The Court identified several key concerns:13

• Religious Mission: The Court determined that parochial schools were an integral part of the religious mission of the Catholic Church, making it difficult to separate secular education from religious instruction.1
• Oversight Challenges: There was significant concern regarding the level of government oversight required to ensure that public funds were not being used for religious purposes, which would necessitate intrusive and ongoing monitoring.1
• Political Division: The Court feared that state support for specific religious institutions could exacerbate political divisions along religious lines.1

While the Lemon test was used for decades to adjudicate establishment clause cases, it was explicitly rejected by the Supreme Court in 2022.2