The hope of social mobility through success in this system was the motivation for going to school in the first place, whether one was the son
of a scholar or a farmer. But even for the farmer's son who did not do
well enough to take the exams even at the lowest level, going to school
had the major payoff of working literacy, and this literacy was acquired
through mastery of the same basic texts that others who went on to
pass the examinations at the highest level also studied. This curricular
uniformity had an extremely powerful effect on Chinese society, and the
major impetus for this uniformity was the meritocracy promoted by the
civil service examination system.

This text states that success on the civil service examinations
was

"dependent only on one's ability rather than one's social position."

What does that mean?

This quote means