Since the belief in a deity is often a philosophical question, atheism is the branch that theorizes their is no god. Humanism is something completely different in my mind.
Could you not indoctrinate a child from birth to reject the very notion of god? The same way as you indoctrinate them to believe in god? Many children will accept parental socialization, others reject it.
I rejected the notion of god from an early age despite my parent's best efforts. Santa Clause was better anyway, he brought me stuff.