R and RR are among the sounds a child acquires latest, and there is a physical reason: they require precise, coordinated tongue movement that develops after the simpler sounds. A three-year-old who replaces R with L is therefore not automatically a cause for concern.
Why I will not give you an exact age
It would be easy to write a number, and there are tables that do. But the order and age at which sounds are acquired varies from child to child, and an age quoted out of context does two kinds of harm: it reassures the parent who should come, and alarms the parent who has no reason to. The expected age for your child is one of the concrete facts an assessment provides.
What is actually worth observing
- Is the child understood by people outside the family?
- Is R the only sound affected, or others alongside it?
- Have they started school with the sound still missing?
- Is the child suffering for it - avoiding words with R, withdrawing from conversation?
- Is R distorted, rather than simply substituted?
A yes to the third or fourth point is reason enough for an assessment, regardless of the exact age.
How R is worked on
The work follows an order: first the sound in isolation, then in syllables, then in words, then in sentences, and finally in free conversation. That last step is the most important and usually the longest. An R that appears in exercises and vanishes in conversation is not finished work.
Short, frequent practice at home is worth more than one long session once a week - but always with exercises given by the therapist, because a wrong technique fixes the error in place.