Do not educate them, or expose them to critical thinking, logic, or science.
Lie to them constantly about how the world works. Feed them a steady diet of mumbo-jumbo dressed up like real knowledge, and pretend that it is deep wisdom.
Make them loathe their own natural bodies and functions. Convince them they are small and weak and worthless and in need of redemption. Tell them everything enjoyable is grievously wrong to even think about, and that their only fun should be in grovelling to an invisible superior being.
Ensure that they resent anyone who is not like them in every way — skin color, nationality, political opinion, but especially creed. Make such people out to be evil and vile and give them the fictional power to somehow oppress and persecute the majority who do think like you.
Teach them to laugh at and dismiss out of hand any faith but their own.
Instruct them with all severity and import to never question for themselves, to never think for themselves, to never live for themselves, but to seek answers only in one — just one — particular set of semi-literate bronze-age folk tales.
Above all (and this cannot be overemphasized), make sure they cannot spell, use correct grammar, or understand basic English words.
That should do the trick.