They have to learned it step by step living with their peers, in a society, under the wise guidance of educators, in a school that allow imagination and expression. Morality is not intelligence. Intelligence is not morality. Morality is the continuous learning of the proper customs and manners of living within a specific society. There is no real system of morals to be understood.
Morals have to be practiced and then understood.
TO BE KIND is not enough of a rule. FIRM is certainly better if someone wish to speak of moral intelligence.