Evolution is not a proven fact, so it shouldn't be taught as the only possibility.
To support Evolution, you almost have to support an array of things like:
1. all matter exploded out of nothing and created itself and the universe. (how scientific is this?)
2. the earth formed, and by pure chance, an evironment formed which could sustain life
3. life forms at random and just happens to have a waiting environment which can sustain it and feed it.
4. life not only survives, but has the means to reproduce itself and eventually evolve into humans. If the first life form had died before reproducing, that would mean that a different life form came into existance at another time, then was able to survive and reproduce.
What are the odds that,
a. the first life form survived and reproduced?
b. multiple life forms kept popping into existance until one was lucky enough to survice, then reproduce?
Sorry, but the giant leaps of faith needed to believe that the perfect chain of miraculous events all happened in order for humans and life to exist is just as good as saying it was all magic.
I believe evolution has happened within species, but that's it. No way do I believe that life formed by itself and morphed into humans and everything else.
Intelligent design is just as viable an angle for pursuing answers to these events, and it should be taught. Evolution and the big bang cannot be explained by any science. The big bang defies the "laws" of physics that are being taught.
An intelligent creator is just as viable a scenario as saying that all matter created itself out of nothing, then exploded and became what is now our universe and all life within it.