The practice of “redshirting” kindergarten students by delaying their school entrance for a year is not as widespread as previously reported, according to a recent study from the University of Virginia and Stanford University.

About 4 percent of children delay kindergarten, the study found, based on an analysis of national longitudinal data that tracked more than 10,000 infants from birth in 2001 through school entry.

Earlier studies and news reports have estimated national rates between 5 percent and 19 percent or even higher.

The redshirting rate is higher for boys (5 percent compared with 2.5 percent for girls), for white children (6 percent compared with less than 1 percent for black children), and for those from wealthy families (6.4 percent for the wealthiest quintile compared with 2.3 percent for the poorest quintile).

The study found that most children who did delay kindergarten were not likely to struggle in school.

“We went in having the sense that this is probably something that could have a big impact on things like achievement gaps” because delaying kindergarten could give an academic edge to the students whose families can afford an extra year of preschool, said Daphna Bassok, an assistant professor at the Curry School of Education at U-Va. who co-authored the report with Sean F. Reardon of Stanford.

“But we wanted to see, what do the numbers really say,” she said.

They found the national redshirting rate is not large enough to exacerbate achievement gaps.

From community to community, however, the effect could vary, Bassok said. The report cites a 2000 study of Wisconsin school districts that showed redshirting rates ranging from 3 percent to 94 percent.

Concerns over the past few decades about growing academic pressures in the first official year of school have sparked an interest in extending the more creative and care-free preschool years.

Some parents consider delaying school if they think it will help their children be more successful academically, socially or athletically. And there is some research to support this approach, showing that older children are more likely to hold leadership positions later in their school careers.

Other studies have shown, however, that children can benefit from learning from older students in their class.