Both should be taught, I agree, BUT on entirely differt grounds.
Evolution as science with an exceptionally firm scientific and testable footing, albeit not 100% unproblematic. Creationism as part of teaching about religious beliefs, where all major world religions as well as Atheism and Secular Humanism should receive their share of the time. Also the debate on creationism and evolution in itself can serve as an example of a complex issue, where people disagree, and to explain the scientific method.

The "teach both"-argument doesn't hold. Time and resources are limited, the same applies to education. Choices must be made, in this case on a scientific basis. Diversity of views in education isn't paramount: Should education about the holocaust be "balanced" by also teaching theories of holocaust-denial? No of course not. Science and facts (historical accounts) clearly favors the view that the holocaust did occur above the nutjob-theories that deny it. The same goes for evolution vs. creationism.

If you mean as part of science teaching on an equal footing, that is a bit far fetched, given the more or less accepted standards for scientific enquiry and the tiny support of arguments and scientists that creationism has.