Just want to say a couple of things as someone with a strong scientific background in biology who is also deeply religious.
First, biological evolution is the closest thing that the science of biology has to a unified theory for the discipline. Nothing in biology makes sense except in light of biological evolution. That's how important it is. Biological evolution, in effect, accounts for biological diversity as well as life's continued flourishing on a more general level. Put simply, understanding biological evolution is essential to understanding the science of biology. That's why a course in biological evolution is required for college-level biology majors at universities across the country. It should be included at the high school level as well, but often isn't for better or worse.
Second, part of why biological evolution is inadequately covered at the high school level is that understanding it requires a fairly demanding level of prior knowledge in biology more generally. To understand biological evolution, you have to at minimum also understand genetics. You also have to understand ecology. Because biological evolution is all about changes in allele frequencies over time (genetics) in entire populations of organisms primarily in response to environmental conditions (ecology). I'll also add that modern biological evolution is not Darwinism. Modern life scientists only really talk about Darwin in a historical context; the scientific understanding of biological evolution is much more sophisticated and nuanced than what was originally proposed many dozens of years ago.