Evolution is a fact, and schools should teach facts.
The phrase "theory of evolution" does not suggest uncertainty about the fact of evolution any more than the phrase "music theory" questions the existence of music. A theory is a framework by which a known process is understood.
The prevailing theory of biological evolution is Darwin's idea of the hereditary transmission of slight variations through successive generations. Some variations are naturally "selected" due to adaptiveness. Biology makes no sense without recognizing the fact that all species of plants and animals (including humans) have developed from earlier forms. Natural selection has withstood more than a century of rigorous scientific testing.
Creationism, a religious belief, has withstood no testing. Whereas scientists will tell you exactly what would falsify evolution (for example, routinely discovering horse skeletons mixed in with trilobite fossils in the Cambrian strata), creationists never volunteer what set of circumstances, if true, would count against their idea that all species emerged at one time. Since creationism is not assailable, not vulnerable to experiment, it is not science.
The bulk of creationist literature consists of attacks against evolution, pretending that the eradication of the idea of evolution would cause creationism to win by default. The only "evidence" creationists present is the story in Genesis, or other religious texts, that must be accepted by faith, not by rational principles of verification.
Creationism can be discussed in the context of comparative religion, philosophy, politics, or culture. It should not be taught in the science classroom.
Many religious people welcome the fact of evolution, just as they accept the theory of relativity with no threat to their faith. They see evolution as one of the tools their God used in creation.
All human beings, religious or not, should feel enriched by discovering our place in nature and the interconnectedness of all living things. The understanding of evolution by natural selection is wonderfully enlightening to science. It should be loudly and proudly taught.