Teach children about Jesus at a young age,

[robvalue]

You can teach people about the fictional character Jesus portrayed in the bible, that is perfectly valid. It's telling your child that this is an accurate account of real events, which has some relevancy to real life (beyond perhaps some useful messages), which is indoctrination.

Telling your child that many historians believe there was a historical figure around that time at which the stories were based on, is also accurate, and that would be teaching. Telling them Jesus was real beyond doubt, and still is real, is indoctrination.

Telling your kid Santa is real is also indoctrination, although parents generally plan to undo it at an early age. Or to confess it when the child starts asking critical questions.