[P-Marlowe]

It consists of three prongs:

1. The government's action must have a legitimate secular purpose;
2. The government's action must not have the primary effect of either advancing or inhibiting religion; and
3. The government's action must not result in an "excessive entanglement" of the government and religion.

If any of these three prongs is violated, the government's action is deemed unconstitutional.

I would replace it with the common sense test. Does this action by the government establish a religion in violation of the first amendment?

First prong: Is a religion established?
Second prong: Is a religion established?
Third prong: Is a religion established?

[xzins]

The government's action must have a legitimate secular purpose; The government's action must not have the primary effect of either advancing or inhibiting religion; and The government's action must not result in an "excessive entanglement" of the government and religion.

So let's say that I'm a local school board, and I want to buy American History books for the local Baptist high school.

1. Secular purpose: I'd like these kids to get a gov't version of history

2. Advance or Inhibit religion: how could it? it's the textbook our local schools use.

3. Entanglement: nope. it's a purchase, not a marriage.

But we both know they'd never allow the school board to buy textbooks for the local Baptist Church.

They don't even look at their own tests with common sense.

Your new standard should be revised.

1. Does it establish a religion?

2. Use some freakin' common sense.

[Ostlandr]

These are some pretty muddy waters. Also, you left off the second half,
". . . or prohibiting the free exercise thereof."

I see where these "entanglements" can cause problems. One example is the practice of exempting churches from local property taxes as a public service. All well and good- but this puts the State in the untenable position of deciding what is and is not a church. An example might be where a pagan group purchases a plot of land specifically for religious use, but are unable to get the tax exemption since it is not a brick-and-mortar church.
Another trouble spot is allowing clergy to simultaneously perform a civil marriage during the religious ceremony. Makes perfect sense- why make a second trip to see a judge after you've already seen the preacher? But again, this puts the State in the untenable position of deciding who is and is not a clergyperson.