The child is developmentally delayed but making progress.
learning disabled
Frequency:
50
%
She is a learning disabled student who excels in art.
cognitively impaired
Frequency:
45
%
The patient is cognitively impaired and requires special care.
Idiomatic Expressions for mentally retarded
Phrase: mentally retarded one's growth
Meaning: to hinder or impede someone's mental or cognitive development
Usage: The lack of proper education was mentally retarded her growth as a child.