S.H.
it is not only the calcium that is needed... the reason for "whole" milk for kids ages 1-2 years old... is BECAUSE, the "milk fats" in it is an ESSENTIAL nutrient, for Brain Development.
Kids... need healthy fats... for development/growth/brain development.
So, make sure he gets that too.
It is not only about Calcium.
If you give him yogurt.... give him WHOLE MILK yogurt... there are many brands of this for kids.
Don't buy low-fat yogurt for him. Again, they need the milk-fats of whole milk, for Brain development too.