Childhood indoctrination refers to the practice of instilling a doctrine into children who are often too young to think for themselves. This is different from education in that the children are expected not to question what they are taught.
Children are notoriously gullible. As such, telling them that an Invisible Man lives in the sky waiting to send them to Hell will probably be believed whether or not it's actually true, and may constitute child abuse. Richard Dawkins thinks so, anyway.