The Lemon test:

A challenged government program is constitutional if it satisfies all three parts of the 3-part test:

(1) it must have a secular purpose; and

(2) a primary effect that neither advances nor inhibits religion; and

(3) it cannot create an excessive government entanglement with religion.

(1) In applying the Lemon test, there must be a secular purpose, but the secular purpose does not have to be the only purpose or the primary purpose. It does, however, have to be an actual purpose rather than a sham. A sham purpose would be a fictitious purpose that the government has fabricated to avoid its action being invalidated on Establishment Clause grounds.

(2) The effect prong is the most difficult to apply. One explanation for this is that the Court does not use specific and consistent criteria to evaluate effect. Another reason is that the Court often does not evaluate challenged government actions in the public schools under the effect prong because it strikes them down under the secular purpose prong and does not need to reach the effect prong.

(3) Excessive entanglement does not mean the government involving itself with the subject of religion such as by drafting a prayer. Instead it means the government involving itself with the subject of religion and working together with a member of the clergy, a house of worship or a religious organization. Certain forms of interaction, however, are not constitutionally problematic. For example, excessive entanglement does not exist where there is only routine administrative cooperation (filling out forms such as the attendance forms in Zorach listing students who are absent) between a public school and a religious entity. On the other hand, allowing a religious entity to use school facilities during the regular school day to teach religion as in McCollum would be excessive entanglement. In addition, if the government delegates governmental power to a religious entity, the relationship will be viewed as creating excessive entanglement.