When it comes to the matter of schools and evolution, the primary motive for teaching evolution in schools is to attract students to atheism and/or a naturalistic worldview at a early age and in a way that is not easily challenged by many parents. In other words, teaching evolution puts youngsters on a path towards atheism. The better the student, the more positive the reinforcement, and the more likely this approach will attain its desired effect.
William Jennings Bryan, the chief spokesman against evolution, was concerned that teaching evolution would undermine the biblical foundation for moral teaching. He said that Darwinian teaching would give children ‘ … a doctrine that refutes not only their belief in God, but their belief in a Savior and belief in heaven, and takes from them every moral standard that the Bible gives us’. 
If schoolchildren were permitted to believe (and say) that evolution is less likely than intelligent design, it would contradict the philosophical underpinnings of unguided evolution. This would lead students to question, even to reject, such materialist philosophies as atheism and secular humanism.
A more honest way of teaching about evolution would not be to present it as an unquestionable dogma, but simply to tell pupils what it is, how many scientists of various types believe in it; then to present all the scientific evidence for and against it.
Haeckel, a German embryologist, altered drawings of various animal and human embryos, making them nearly identical. He presented his altered pictures as evidence for evolution between species, and used them as a platform to successfully promote evolution. In 1874, Haeckel's drawings were exposed as frauds by renowned embryologist Wilhelm His. Shortly thereafter, Haeckel was convicted of fraud by his own university. Yet his fallacious drawings of nearly identical embryos are still in science textbooks over 100 years later as evidence for evolution! Those drawings are being taught to kids in school today as evidence for evolution. 
For students who are mature enough to understand the philosophical implications, say, beginning with the upper three grades of high school, educators could explain the ideological links between evolution and various philosophical and political schools of thought: materialism, atheism, eugenics, Nietzsche, etc.
Similar links could be explored for ideas which criticize evolution, such as intelligent design which accepts some aspects of evolution while denying the lack of guidance, and creationism, which begins with the premise that God created everything; see young earth creationism and old Earth Creationism.