Is saying high/low (number) wrong?

I got this feedback of "wrong collocation" on my essay.

Here is the line -

The average level of computer ownership in 2002 was in the high fifties (in percentage).

The teacher said that 'high fifties' is incorrect grammar (wrong collocation). I just want to know why and how to correct it.

Solution 1:

There is nothing grammatically wrong with saying "high fifties".

The numbers that are greater then or equal to fifty, but lower than sixty, are called "the fifties". The higher ones are called "the high fifties ". So in the "high fifties" means approximately between 55 and 60.

There is an issue in that "level" is not defined in the sentence. This makes the sentence meaning not completely clear on its own. But if "level" is defined elsewhere, perhaps because all previous levels have been defined in some way, then the sentence is correct. In any case, the sentence is definitely grammatically correct.

If the definition of "level" is not clear from context, then substituting the word "percentage" for "level" makes the sentence clear, self-contained and correct.