Andrew Was Born Two Days Before the School Entrance Cut-Off

Andrew was born two days before the school entrance cut-off date. His parents decide to "hold him back a year," i.e., they decide to delay his kindergarten entrance one year so that he will be among the oldest in his class rather than among the youngest in his class. Which of the following is relevant information that Andrew's parents should consider?

A) Children whose birthdays make them just barely old enough to qualify for school entry obtain higher IQ scores by age 8 than children whose birthdays make them fall just short.
B) IQ is not related to years in school.
C) Intelligent people stay in school longer.
D) Starting school early does not seem to nurture any specific cognitive abilities.