Which of the following would be considered a violation of the Establishment Clause?

A law requiring prayer in public schools is a clear violation of the Establishment Clause, which is part of the First Amendment to the United States Constitution. This clause prohibits the government from establishing an official religion or unduly favoring one religion over another. By mandating prayer in public schools, the government would be endorsing a particular religious practice and compelling students to engage in that practice, which contradicts the principle of separation of church and state. Such a requirement could alienate students who may belong to different faiths or identify as non-religious, thus violating their rights to freedom of belief and expression.

The other options do not violate the Establishment Clause. Allowing students to form religious clubs promotes free exercise of religion, protecting individual rights without government endorsement. Laws protecting freedom of speech and prohibiting discrimination also uphold fundamental rights without infringing on the separation of church and state.