Darwin's theory of evolution and natural selection does not, IMO, constitute a replacement for God.
But that does not mean that the leftist education establishment would not use it in that way. There's a difference there.
Ok, I realize there are people out there who believe in both. But that is not how it is being taught in our schools. They texts are actually attempting to say there is no need for God. That may not have been Darwin's intent--that is up for debate--but it is certainly the attempt of many of the text book writers.