I came across a fascinating article from the New York Times that I am sure many of you would consider good food for thought about what age to start your child in kindergarten:

AFTER all those attentive early childhood rituals — the flashcards, the Kumon, the Dora the Explorer, the mornings spent in cutting-edge playgrounds — who wouldn’t want to give their children a head start when it’s finally time to set off for school?

Suzanne Collier, for one. Rather than send her 5-year-old son, John, to kindergarten this year, the 36-year-old mother from Brea, Calif., enrolled him in a “transitional” kindergarten “without all the rigor.” He’s an active child, Ms. Collier said, “and not quite ready to focus on a full day of classroom work.” Citing a study from Malcolm Gladwell’s book “The Outliers” about Canadian hockey players, which found that the strongest players were the oldest, she said, “If he’s older, he’ll have the strongest chance to do the best.”

Hers is a popular school of thought, and it is not new. “Redshirting” of kindergartners — the term comes from the practice of postponing the participation of college athletes in competitive games — became increasingly widespread in the 1990s, and shows no signs of waning.

In 2008, the most recent year for which census data is available, 17 percent of children were 6 or older when they entered the kindergarten classroom. Sand tables have been replaced by worksheets to a degree that’s surprising even by the standards of a decade ago. Blame it on No Child Left Behind and the race to get children test-ready by third grade: Kindergarten has steadily become, as many educators put it, “the new first grade.”

What once seemed like an aberration — something that sparked fierce dinner party debates — has come to seem like the norm. But that doesn’t make it any easier for parents.

“We agonized over it all year,” said Rachel Tayse Baillieul, a food educator in Columbus, Ohio, where the cutoff date is Oct. 1. Children whose birthdates fall later must wait until the next year to start school. But her daughter, Lillian, 4, was born five days before, on Sept. 25, which would make her one of the youngest in the class.

With the wide age spans in kindergarten classrooms, each new generation of preschool parents must grapple with where exactly to slot their children. Wiggly, easily distracted and less mature, boys are more likely to be held back than girls, but delayed enrollment is now common for both sexes.

“Technically, Lillian could go to kindergarten,” Ms. Tayse Baillieul said. Moving her up from part-time preschool would allow Ms. Tayse Baillieul to return to work and earn income. But Lillian’s preschool teachers counseled her to hold Lillian back. “They said staying in preschool a year longer will probably never hurt and will probably always help, especially with social and emotional development.”

Regardless, a classroom with an 18-month age spread will create social disparities. “Someone has to be the youngest in class,” pointed out Susan Messina, a 46-year-old mother in Washington. “No matter how you slice it.” When Clare, her daughter, who is now 9, entered kindergarten at 4, Ms. Messina was aware of widespread redshirting.

“I thought, I’m not breaking the rules, I’m not pushing her ahead, we’re doing exactly what we’re supposed to do,” she said. “Then it dawned on me that in this day and age, there’s a move to keep your brilliant angel in preschool longer so they could be smarter and taller for the basketball team. But my daughter doesn’t need a leg up. She’s fine.”

Still, it bothers her that children in the same class are as much as a year and a half older than Clare. “She has friends who are 11 who are going to get their periods this year, and she’s still playing with American Girl dolls.” Another mother complained that her 4-year-old became hooked on Hannah Montana by her aspiring-tween classmates. A 6-year-old wielding a light saber can be awfully intimidating to a boy who still sleeps with his teddy.

At the other tip of the age span, parents who promote children to kindergarten before 5 are often seen as pushy, “even ogre-ish,” Ms. Messina said. But suppose your child is already reading at 4? Do you hold her back where she may be bored to tears in preschool or send her into a classroom of hulking 6-year-old boys? In 1970, 14.4 percent of kindergartners started at age 4. That figure has dropped to less than 10 percent.

The self-esteem movement has inspired parents to care as much about emotional well-being as academic achievement, and with fragile self-images still in the making, the worst fear for parents is setting up their children for failure. One Connecticut mother in Fairfield County sent her October-born son to kindergarten at 4, despite “the informal rule of thumb that everyone holds back their September to December boys.” Kindergarten seemed to go well, but when her son entered first grade, she said, “I got hit over the head. They told me he was way behind.”

She watched in horror as her son’s self-confidence tanked. “He was spinning his wheels just to keep up,” she recalled. “He even got pulled out of class for poor handwriting.” At the end of a miserable second-grade year, she withdrew him to repeat the grade at a private school. “It’s been a long and difficult journey,” she said. “I totally regret starting him on kindergarten at 4.”

Many parents feel compelled to redshirt by what they see as unreasonable academic demands for 4- and 5-year-olds. But keeping children in preschool, according to both academic research and parental experience, doesn’t necessarily offer every advantage. Jennifer Harrison, a mother of two from Folsom, Calif., held her October-born son, Elliott, back so he “wouldn’t get labeled as out of control.” Over all, she said, it was the right decision. “But his math skills are far above those of his classmates.”

How to attend to a child’s myriad needs, and which should be the priority? “There don’t seem to be any rules,” said Rebecca Meekma, a mother of two from Laguna Beach, Calif. “People are saying, ‘I want him to be big in high school for sports!’ What is that? You can’t know who they’ll be in high school.”

And what about children who aren’t Leo the Late Bloomer? “I have met mom after mom who is intentionally holding her child back a year,” said Jennifer Finke, a mother of two in Englewood, Colo. “They say they don’t want their kids to be the youngest or shortest. Is that right? Is it fair?”

Ms. Finke’s son, Benjamin, is soon to start kindergarten at 5. “There will be boys in his class who are a year or more older than him. They’ll be bored in class and then the bar will be set higher, and the kids who are the right age will find that they can’t keep up.” What will happen in gym when the larger boys are picked first for brute force, leaving the pipsqueaks languishing? “I’m afraid my children will feel inferior.”

Not all parents can choose when their children begin kindergarten. “Though redshirting is common in the suburbs, in Manhattan, it’s the schools — not parents — who decide,” said Emily Glickman, whose company, Abacus Guide Educational Consulting, advises parents on kindergarten admissions. At New York City private schools, the cutoff date is Sept. 1; in practice, summer babies, particularly boys, generally enter kindergarten at age 6. “It’s a ramped-up world,” Ms. Glickman said. “And the easiest way for schools to assure that their kids do better is for them to be older and more mature.”

Meanwhile, New York City public schools have a firm age cutoff date of Dec. 31. Kindergarten isn’t required by the state, so parents could keep their children out, but then they would have to start the following year at first grade. And not everyone can afford two to three years of nursery school or day care.

“Among parents here, there’s a tremendous demand for kindergarten earlier,” said Eva Moskowitz, founder of the Harlem Success Academy Charter School, which pushed its cutoff back to Dec. 1. “If these parents could start their kids at 2, they would.” Not everyone, alas, defines academic privilege the same way.

In an earlier version of this article, there was an incorrect reference to the Malcolm Gladwell  book that contained a study of Canadian hockey players.