My experience was not uncommon. Scholar Patrick Glynn has described how he took a similar path that ended up in atheism:
I embraced skepticism at an early age, when I first learned of Darwin's theory of evolution in, of all places, Catholic grade school. It immediately occurred to me that either Darwin's theory was true or the creation story in the Book of Genesis was true. They could not both be true, and I stood up in class and told the poor nun as much. Thus began a long odyssey away from the devout religious belief and practice that had marked my childhood toward an increasingly secular and rationalistic outlook.