Why is evolutionary biology challenged today in schools?

Because some religious persons feel it conflicts with their teachings, although I personally see no conflict. It's back to the ol' separation of church and state thing.

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Only micro-evolution has been observed in bacteria and viruses. Some of that like virus strains changing each year is more like simple change over time rather than micro-evolution. The fossil record demonstrates stasis and a distinct lack of transitional forms, hence the need for "punctuated equilibrium"; for which the evidence is lack of evidence. Genetic analysis and homologous structures do not always line up.

Far from being essential the theory of evolution has actually contributed very little to scientific progress. The only area in which it is essential is evolutionary biology, regular biology can manage without it. Where are the advances for which the theory of evolution has been essential?

Edwards v Aguillard already ensures that teaching pseudo-science is illegal so it's best to just ignore them. Someone already posted that it's pure abject stupidity.

And yet the Left ignores hundreds of years of Political and Economic science in exchange for Political and Economic dogmas that have proven demonstrably repressive and damaging to the Human Race.

Well my opinion is that some people reject the evolutionary theory because it contradicts their religious beliefs.

I agree that it's essential.

I was taught evolution throughout school, every single year.

Conservatives cannot afford their children being taught to think of the world beyond what is taught in church.

Religious people are freaking stupid.

excellent point