Early in his book Outliers, Malcolm Gladwell presents statistics about hockey players. Those born near birthday cutoff dates are older—and therefore bigger—and have a better chance of getting picked for more elite teams.
The same basic principle applies for students attending school and their academics.
Children born a month before the September cutoff date compared to children born 10 months before the cutoff date are mixed together in the same class. The older student have a large age lead on the younger students, which is a significant difference, especially in little kids.
Cognitive and decision making abilities are far more advanced in older children, making them able to learn and understand the world around them more easily. Due to this age and knowledge difference, students might be separated into advanced and regular classes unfairly, causing problems later.
There is some debate among parents and teachers over the benefits of holding back children a year to prevent them from being the youngest in their classes. This decision might seem drastic to some, but the upsides of being the oldest in each grade continue throughout a student’s school career.
Even now in high school, where everyone is caught up academically, it is a hassle to have to get a learner’s permit and driver’s license a full year later than everyone else. Being younger also makes getting internship and job opportunities for college applications more difficult because most companies and organizations have age cutoffs. It is difficult to be fully accepted while being significantly younger than classmates.