phrases - What is the correct use of "at the age of" or similar for describing a group of people?

Recently, for a scientific publication, I wrote something like the following:

The sample consisted of all students at the age of 13 years or older.

However, I received this back from the language check changed into the following:

The sample consisted of all students who were 13 years of age or older.

While I see that the second versions indeed sounds a little nicer, I was wondering if the first version would be correct from a grammatical point of view when it is used for describing a group of people as opposed to, say, for describing the age of a person at which an event has occured.

Can I use "at the age of" for describing a group of people? If not, would anyone able to clarify the correct use of this phrase?

Answer

Since this is a scientific paper, if you wanted to include the number, you could also say "consisted of all students who were 13 years of age or older (n=158)."

A phrase often used to describe an age group is cohort:

(definition 6)
a group of persons sharing a particular statistical or demographic characteristic: the cohort of all children born in 1980

Here is a picture using "age cohort" to illustrate.

So I might rewrite the sentence as:

The sample consisted of all students (n=158) in the age cohort over 13.