A U.S. District Court in California has ruled that it's unconstitutional for a public school teacher to say that creationism is superstitious nonsense. According to Supreme Court precedent going back to 1984, the Establishment Clause of the U.S. Constitution doesn't mean merely what it says (which is just that the government can't set up a state religion) but extends even to government employees saying something that a reasonable person might take to count as endorsement of a particular perspective endorsing or disapproving religion. Add to that the conviction that creationism is religion, and you get this result. This does seem to me to be a direct application of current Supreme Court precedent and the standard view of creationism as religion (which the Supreme Court has endorsed, at least in one instance of the use of the term and a U.S. appeals court has declared to be applicable to intelligent design as well, although that judgment is only legally binding in one of the three federal court districts of Pennsylvania, just as this current decision is only legally binding on one of four federal court districts in California). [For the record, my detailed evaluation of the last case is here.]
Now I don't happen to think this is the right result, for several reasons. For one, the term 'creationism' can mean a lot of different things. It could mean the view that the the Earth is 6,000 years old, more precisely known as young-earth creationism. Some hold this view because they believe scripture teaches it, in which case it counts as a religious belief. Others claim to find it taught by science, in which case their support for it is of the kind that should count as science, even if it's bad science. The Supreme Court has declared that since it is taught in scripture, and science the scientific reasoning being presented is not good science, it can't be of the kind that should count as science. That claim has always seemed wrong to me, and I think this result is exactly what follows when you take such a view. If it's not of a scientific kind, then deriding it as bad science is also not of a scientific nature but of a religious nature (even if it's against a religious view).
But the term 'creationism' can also mean simply that there's a divine being who created. That's often a religious belief. It can also be a philosophical conclusion of arguments that have been present throughout the entire history of Western philosophy and have been held alongside religious beliefs by some but independently of religious beliefs by others. Thomas Aquinas, for example, presented arguments for God's existence that did not rely one bit on any religious beliefs. Lots of thinkers have believed in a creator without thinking they have any religious obligations to that creator. So even that kind of creationism isn't clearly religious, although it often is. Intelligent design arguments fall into this category if they conclude with the belief in a divine creator (rather than a more open conclusion, e.g. merely that there is some designer, which could be aliens if we're talking about biological ID arguments rather than cosmological fine-tuning ID arguments).
When a teacher says that creationism is superstitious nonsense, absent a context, it's not clear what that teacher means. It's certainly not obvious to me that it's a derision of particularly religious elements in any particular one of these things creationism can mean. But I do suspect that most people saying something like this aren't going to be sensitive to any of the distinctions I've just outlined, and they probably do intend to think of creationism as a religious teaching. Given some of the other statements this particular teacher made, I think this is especially likely in this case.