The Lemon test:

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

(1) it must have a secular legislative purpose (that is not a sham); and

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

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

(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 fictitous 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. The government is unlikely to be viewed as advancing religion if it distributes a neutral benefit (such as free bus transportion or school lunches) broadly to a wide range of beneficiaries that include all schoolchildren (whether they attend public or private schools and whether the private schools are religious or nonreligous schools). Passive displays are unlikely to have the impermissible effect of advancing religion so long as they are not in a public school.

(3) Excessive entanglement involves the government working together with a religious entity. Certain forms of interaction are not constitutionally problematic. For example, excessive entanglement does not exist where there is only administrative cooperation (filling out forms, providing financial information, occasional inspections, etc.) between the government and a religion or a religious entity like a parochial school. On the other hand, pervasive monitoring of the actions of a religious entity by the government 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.