Using NAPLAN test results of 5,000 year 3 students, researchers from the University of Melbourne found the delays were equivalent to a child missing about 35 days of a school year.
Melbourne University's Cain Polidano described the findings are relatively small but significant.
"There is already a bit of evidence that shows that caesarean birth is related to a number of negative childhood health outcomes, including risks of ADHD, autism and also asthma", Dr Polidano said.