By the time the child is six years old, moral education ought to be nearly complete ; that is to say, the further virtues which will be required in later years ought to be developed by the boy or girl spontaneously, as a result of good habits already existing and ambitions already stimulated. It is only where early moral training has been neglected or badly given that much will be needed at later ages.
Source: On Education, especially in early childhood, 1926, by Bertrand Russell
More info.:
https://russell-j.com/beginner/OE04-010.HTM
#Bertrand_Russell