Salt Lake Tribune — Amanda Moody began thinking about when to enroll her son in kindergarten soon after he was born on a late summer day.

She and her husband eventually decided it would be best for Asher to start kindergarten this month after he turned 6 on Aug. 1 rather than a year ago, when he would have barely turned 5 by the first day of school.

Research and friends’ opinion were split. “I did kind of waver a couple of times,” she said. “For boys especially, I think that socially they can use that extra year at home before they are put into a group of other kids where they are expected to share and interact socially.”

Moody joined the growing national trend of parents who “redshirt” kindergartners -- a term borrowed from athletics -- holding them back from school until they turn 6. Parents may hope that being an older student will give their child an edge in academics, sports or leadership, now or in the future. Others, like Moody, want to make sure their child is socially ready and mature enough to handle school.

Some statistics estimate kindergarten redshirting has tripled since the 1970s.

The National Association for the Education of Young People advises against redshirting. In a 2003 review of the research, it questioned the supposed benefits.

While the oldest children in a class are more academically successful early in elementary school, the paper said, those differences usually disappear by third grade. Research has found no difference between younger and older students in their self-concept, peer acceptance or teacher ratings of behavior, though younger children were less likely to be nominated as well-liked by their peers.

While studies have shown some redshirted children worry they have failed and have poor attitudes about school, that may not be the case among middle- to upper-income students, according to the review. It concluded that holding children back may deprive them of important opportunities for learning.

In other research:

-- A 2000 review in the Clearinghouse on Elementary and Early Childhood Education said evidence on the effects of redshirting is mixed. Some kids who were redshirted because they were thought to be immature, it added, were later found to have special needs that could have been addressed earlier.

-- A 2011 study published by the Center for Education Policy Analysis at Stanford University estimated that 4 percent of children delay entry into school. Most often, they are white, male, from wealthy families and have birthdays in the months before school starts.

Parents who delay kindergarten typically are not worried about their child’s social or academic skills. The Center for Education Policy Analysis study suggested parents do it because they’re worried about their child being younger than classmates and their physical development.

The advantages are obvious when parents want their child to play sports, said one of the authors, Sean Reardon, education professor at Stanford.

But there isn’t enough evidence on the academic side, he said in an interview. And parents may forget that delaying school means one less year in the workforce, he said.

He also noted that redshirting can affect classrooms and disadvantage children who didn’t delay -- such kids often are from low-income families who can’t afford to keep them home.

If the classroom age is skewed higher, “the kindergarten teacher might aim the level of instruction a bit higher. ... That can make it harder for those kids younger and most behind to catch up,” he said.

But Canadian researcher Elizabeth Dhuey believes there are lasting academic advantages. An economist at the University of Toronto, she has studied the school start dates of thousands of children in 19 countries. She believes kids who begin classes later often perform better on tests later and are more likely to attend college.

Roseanne Bowles has never regretted waiting until her daughter, Marie, was 6 to enroll her in kindergarten. Bowles wanted Marie and her younger sister to be two years apart academically so they could attend the same schools together.

Now in seventh grade, Marie is thriving, Bowles said. “I am really glad I did it because she is at the top of her class. ... I think she is better off.”

Bowles wishes she had done the same for her sons, who have both graduated. With birth dates in July, they were among the youngest in their classes.

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