I anticipate some flak coming my way on this point after Tea Partiers read below that I criticized Christine O'Donnell. So here is a brief refresher for those among you who see grave Constitutional peril in a particular semantic. The First Amendment does not contain the words "separation of church and state." So too will you search in vain in the Constitution for the word "federalism," but there is no doubt in anyone's mind that federalism is what the Tenth Amendment is all about.
There is no guarantee in the Constitution for your right to cross-examine witnesses against you. The closest you get to that is the Sixth Amendment which provides that you have the right "to be confronted with the witnesses against" you. That means you have the right to be in the same room as them when they testify against you. The right to "assistance of Counsel" in the Sixth Amendment does not mean that your attorney can cross-examine the witness, either. But no sane person would contest the claim that the concept of "due process" in the Fifth and Fourteenth Amendments includes the idea of cross-examination.
What this means is that textual literalism is inadequate to understand the Constitution. Is "separation of church and state" a concept in the Constitution? You can argue "yes" or "no," but it's not a dead-bang winner either way simply because those exact words are not there. You've got to look deeper than that, no matter which conclusion you want to reach.
What we know for sure is in there is a prohibition against an establishment of religion,* and a prohibition against governmental interference with the free exercise of religion. I have a hard time understanding the logic of someone who would dispute the idea that the government must be neutral in regards to religion; it must neither favor nor condemn any particular religion as opposed to another; it may neither favor nor condemn religion generally over non-religion. Instead, individuals must be free to believe (or not) as they wish on an individualized basis. This is called "non-endorsement." Non-endorsement and separation of church and state are functionally the same thing; it's just that one phrase has become politicized and the other has not. But the concept is what we're trying to look at, not the semantics.
It remains beyond me how religious people can realistically claim that the government prohibits their right to engage in free exercise in this day and age. This claim usually seems to point to things like state recognition of homosexual couples (whether in the form of civil unions, domestic partnerships, or marriages); complaints about requirements that parochial schools teach biology (what is to say, they object to the teaching of evolution); sex education; and education about and official pleas for tolerance of minority religions, ethnic groups, and sexual preferences.
I do not understand, and have never understood, how any of that interferes with someone's decision to not engage in or believe in any particular religious teaching. "The school said I have to be nice to the gay kids!" Well, yes, you do. Even if your religion says that the gay kids are inherently morally wrong, you still have to be nice to them -- because beating them up for being gay is still beating them up, and you aren't allowed to beat up anyone for any reason. That's called "assault and battery" and prohibiting assault and battery is not a restriction on the free exercise of religion. (There are some anti-bullying measures out there right now which raise my eyebrows -- not because they interfere with the free exercise of religion, but rather because they potentially interfere with free speech. But this isn't the place for me to get in to that issue and I haven't thought it through all the way anyhow.)
The real question that gripes about "separation of church and state" are aimed at can be phrased in an equally valid fashion: how do we appropriately define an "Establishment" of religion? For instance, is teaching creationism in a public school an Establishment of religion? You might argue "no," but I think that's a steep uphill fight -- a public school teacher saying "It is acceptable to believe that God created the universe and God created human beings" is inherently a governmental endorsement of a particular religious belief by the government.
The teaching of evolution as part of biology, however, does not represent a governmental endorsement of atheism or secularism in contrast to religious beliefs. It represents governmental endorsement of science. Plenty of scientists who believe in God also believe in evolution. There is no inconsistency between religious belief and scientific acceptance of the overwhelming evidence of historical macroevolution of biological species.
Yes, "intelligent design" is creationism -- if you want intelligent design taught in public schools, you want to lead public school children down the path to concluding that the "intelligent designer" was Jehovah. Please don't insult my intelligence by offering the fiction that you posit with any degree of sobriety that life on Earth might have been originated by time travelers or long-dead alien genetic engineers.
Another argument that teaching evolution interferes with free exercise is pointing to statistics that Christian children who study evolution leave Christianity in larger numbers than those who do not. If that is really the case, bear in mind that it's not the government saying that Christianity is false, it's the government saying science is important to learn. As mentioned above, there are hundreds of thousands, if not millions, of people who study and teach evolution and nevertheless maintain their religious faiths.
And yes, it is for the United States Supreme Court to have the final say on that question -- someone has to have the final say, and even if you object in theory to the idea that the Supreme Court can "make" law, you would surely agree with Robert Bork and other originalists that the Supreme Court can legitimately interpret the law, that their job is to apply the law to a particular set of facts in the cases that come before them, and that in so doing they set precedent to be studied, considered, and absent a powerful reason not to, followed in future cases.
A moment's thought about what it is that courts actually do reveals that the difference at that point between interpreting, applying, and setting precedent and "making law" is a good deal blurrier than it might have seemed to be at first glance. Precedent is law, because it binds future inferior courts to follow it, and the creation of precedent is inherently part of the "judicial power" which is explicitly granted to the courts in Article III.
So it is quite in harmony with the Constitutional scheme of separation and division of powers for the courts to respond to challenges in appropriate cases by pronouncing when something is or is not an Establishment of religion. When it is, those things should be stricken down by the courts and the exercise of judicial power is not a usurpation of democracy but rather a guarantee of our individual and collective liberties. Those who find the rulings distasteful should nevertheless bow to the orders and reasoning of the courts, because to do otherwise is to invite lawlessness and we are, ultimately, a nation under the rule of law.
To say that there is no such thing as separation of church and state because that phrase does not appear in the Constitution is remarkably shallow thought. Which is why a room full of law students laughed at the suggestion that separation of church and state is not found in the Constitution.
* I suppose you could argue that there is only a prohibition against a Congressional Establishment; if that is your position, would you be comfortable with the idea of a Presidential Establishment of religion? Where in Article II is the President given authority to Establish a national religion?