And that question is the very interesting field of abiogenesis, filled with many theories, and obviously, since the origin of life was over 3 billion years ago, determining which of them is correct will be quite difficult as the surviving evidence of life at that time is spotty.
There's really no need to teach anything about abiogenesis in High School or Junior High given the uncertainty over it and the complexity of discussing it, and I'd have no problem with the whole topic being ignored. However, evolution is a different story.
Is this another theory taught as fact in our public schools?