Age is just a number

Sa
What would happen if we stopped counting years? What would happen if we no longer relied on age to determine where a person "should" be in life?
For example, instead of sending a child to school when he's "5 years old", we would send him when he's ready. 
Or, instead of subconsciously judging a 10 year old girl who is more developed than her peers, we would assume she is older. 
Instead of shaming a 24 year old for not being married yet, well, we wouldn't know her age. So there would be no concrete way to shame her.
What are the pros and cons to this way of thinking?

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