On this question, use the process of elimination.
A) the excerpt does not focus specifically on measuring potential, so you can cross this out.
B) the excerpt does not mention segregation, and though it may be referring to it, it is not the main point. Cross this one out.
C) the excerpt does point to the vitality of equal education, so put a hold on this one.
D) the excerpt talks about the importance of school in general, not high standards. Cross this one out.
The correct answer would be:
C) to highlight the significance of equal access to education.