Parents fear that religion will make their children outcasts 

If you decline to pass your religious beliefs on to your children because you think such beliefs could hurt them socially then there is no meaningful sense in which you actually hold any religious beliefs. No one who actually believes that Jesus is Lord, or that there is one God and Mohammed is his Prophet, would decline to explain that to their children for fear that the children would be made fun of. What such parents are actually saying is that they were raised within certain social practices, some of which happened to be religious, that they see no advantage in their children continuing.