In English, the closest we have is to compare to expectations with peers at various grades in school. For example
He had some developmental delays and still speaks at a first-grade level.
In America, children typically begin kindergarten at five years of age, so first graders are six or seven years old. Speaking-age children younger than five are said to perform at preschool level.
We also gauge reading levels in this relative fashion that can go up or down, as in
She is a bright child. Although still in elementary school, she is already reading at high school level.
As an aside to your question but relevant to the example above, the rough groupings of grade levels contain some cultural ambiguity. Although some American regions still group grade levels into the following, they are now considered a bit dated or old fashioned.
- elementary or primary school (first grade through sixth grade)
- junior high school (seventh through ninth)
- high school (tenth through twelfth)
My parents still refer to levels in these terms—except for my mother sometimes because she is a schoolteacher who went through one way but works in the other. Nowadays, the common groupings are
- elementary school (first through fifth grades)
- middle school (sixth through eighth)
- high school (ninth through twelfth)
