Right, but parents have to think whether the advice is general or religious. It doesn't matter if they think it's true, they should see if the same advice holds for all religions. Praying to Jesus, even if true, is not philosophically independent. It's not good advice for a Muslim, Hindu, or atheist. Eating veggies is never going to be bad advice.
See that doesn't work because that assumes all the advice, practice, and philosophy of all religeons should sync up and all the advice, practice, and philosophy that doesn't work with each other doesn't count.
But if you believe one of these to be true, naturally contradictions between religeons will pop up.
For instance, it is mandatory for Musilms to pray 3 times a day toward Mecca. If a Muslim parent teaches their children this, is it wrong since it doesn't work for Christians or Hindus?
Or how about an athiest parent teaches their kids that there is no God, and that they should never pray. Is this wrong because this doesn't sync up with the Buddhists or Pagans?
Parents teach their children what they know or believe to be true. This is not wrong, and is in fact good in most cases. It's part of the freedom of religeon thing that America has going.