should they teach a variety of theories, and simply say "these are the various explanations" that we have, but a general consensus has yet to be determined?
Depends on the grade level...but I would say they should teach the various
scientific explanations for the origin of life, but they should be very clear in stating that these are ideas or hypotheses, not theories, and that we may never know exactly how life started on Earth because there was little to no evidence left when it happened.
They might even say that various religions have their own explanation, and if they would like to know more about those, they can take a comparative religions course (assuming the school offers one) or they can ask their parents or ministers about the one their religion prefers.