College football fans are no doubt familiar with the term “red-shirting.” This practice occurs when a player participates in an academic year but not in that year’s sports season, extending his or her eligibility to play sports for another year. This usually happens during a player’s freshman year, giving them a chance to mature physically and become better adjusted to the academic rigors of school.

A similar phenomenon happens with young children: some families choose to wait until their kids are 6 years old to start kindergarten. This presumably ensures that they are mature enough, physically or academically, for school. These “academic red-shirts” make up a large number of children below modal grade, or the typical grade for people their age. For instance, the modal grade for 6-year-olds is first grade.

Overall, in 2008, the majority of students ages 6 to 17 (65 percent) were enrolled at their modal grade, with 19 percent enrolled below modal grade and 16 percent enrolled above. There were large demographic differences, however, with boys more likely than girls to be below modal grade (22 percent compared with 16 percent).

Interestingly, foreign-born students were more likely than native-born to be enrolled below and above modal grade.

Enrollment below modal grade can occur because of late entry into school but also because of students repeating grades after entering school. Repeating a grade is most common at kindergarten, first grade and ninth grade.

Kurt Bauman, Chief, Education and Social Stratification Branch, U.S. Census Bureau