Evolution is theory not science. Science is about what can be observed, tested and repeated.
So astronomy isn't within the realm of science either? Sure it is, because astronomers can generate theories about what they observe, generate predictions based on said theories, supported by what we know about chemistry and physics, and those theories and predictions can then be tested and potentially supported or disproved. Same with the theory of evolution. Theories and predictions about evolution are tested by further discovery in fields like paleontology and genetics.
For example, Darwin predicted, based on his theory, that a fossilized species would be discovered in a strata beneath which no modern bird fossils have ever been found, indicating an archaic bird species with differentiated finger bones. Within Darwin's life time, such a fossil was in fact discovered in strata just beneath the point where there were no modern bird fossils ever found. This is a prediction based on a theory supported by observation that was fulfilled by further discovery. That's science, and it happens all the time vis a vis evolution.
It's also science because it's subject to disproof by a discovery which contradicts it, such as the discovery of a horse fossil in Cretaceous strata. Such a discovery would entirely disprove the theory. So far, no evolution-theory-contradicting discovery has been found in undisturbed strata. Were evolution false, that would be a common discovery. Its not having been discovered further supports the theory, since consistent with the theory.
Being disprovable by further discovery places evolution theory firmly within the sphere of science.
