Comparing apples to oranges.The sentence has a deep meaning.
Both apple and orange are fruits but have different qualities and taste. One can't eat an orange in place of an apple. Similarly in our life too, we can't compare our kids with others as our kids may not have the same qualities as others.
Kids who are obedient, sincere and good in studies are considered the benchmark and other kids are compared with them which I feel is wrong. One shouldn't do that. Instead, we should try to improve the qualities of our kids.
It is not just about kids only and is applicable in other cases also. Comparing an apple to another is justifiable but can we justify the comparison between an apple and an orange? Just give it a thought.