When Griffin Hunt was 2 years old, his mother was already worried that sending him to kindergarten when he turned 5 would be a mistake. Griffin, who turns 5 in August, would be among the youngest students in his class.

"Boys are not ready," Jennifer Hunt said. She and her husband have opted to hold Griffin out of school for a year.

"Girls are much better at sitting down and listening and doing their work at a table," she said.

Watching Griffin, who likes to move around, touch things and pick them up, Hunt believes they have made the right decision for the long-term education of her son. They are seeking a "structured pre-kindergarten" program for him to attend next year.

"We don't want him to start out having a negative experience," she said. "We don't want to set him up to fail."

It's a decision many parents of 5-year-olds will be wrestling with in the next few months as they decide where to send their children next fall.

About 9 percent of 5-year-olds nationwide are "academically redshirted," or held out of kindergarten for a year, according to the National Center for Education Statistics.

To be eligible for kindergarten children must be 5 years old on or before Sept. 1 of the current school year.

The redshirts will enter school at age 6, sometimes 18 months older than their classmates.

Academic redshirting is a result of higher expectations of kindergartners, some educators say, and makes sense for students with summer or early fall birthdays, or for ones, usually boys, too immature to handle kindergarten.

While some parents and teachers praise the idea, education researchers fear that holding students back can hinder them socially as they reach their early teens. They also say kindergarten teachers must educate all children, regardless of their level of readiness.

"A group of 5-year-olds are always going to include children who are a little behind their peers, and some who are a little ahead," said Alan Simpson, spokesman for the nonprofit National Association for the Education of Young Children, an association of early childhood educators. "Through natural development, they will catch up with each other."

The term "redshirting" originally described the practice of holding back a freshman college athlete for a year. The belief was that muscles would be more developed, and with an additional year of training, the student would see more success on the field.

Academic redshirting is the same idea, but at a younger age. The extra year gives children's brains a chance to become more developed, theoretically leading to future success in the classroom.

The practice may be in response to higher expectations for young students. Kindergarten used to be a program to transition children from family to school, said Lynn Buffington, lower-school director at St. Vincent's Cathedral School in Bedford, Texas, and a career early childhood educator. But the demand that schools produce high test-scores has prompted a more strenuous kindergarten curriculum including reading, phonics and basic math concepts.

In a national survey in 2000, kindergarten teachers said 48 percent of their students were unprepared, according to research by Lilian G. Katz, co-director of the Early Childhood and Parenting Collaborative at the University of Illinois at Urbana-Champaign. Half of the students lacked academic skills and were unable to follow directions or work independently.

Academic redshirting has become common for students with birthdays in the latter half of the year, and particularly for Anglo boys. It's found more often in wealthier communities, according to Katz, and in private schools.

But the practice is growing in public schools.

Hunt's reason for redshirting her son is common. In fact, other parents who have delayed their children have echoed her fears.

Many educators support the parents' decision.

A child's readiness for school, Buffington said, is often based on a number of intangibles, like the ability to cooperate with classmates or follow directions. Their motor skills may not be as refined as their peers'. Sometimes, it depends on personality.

"If everything is just right, a kindergartner soars," Buffington said. "But innately, parents can sense whether that child is not ready to go on."

Brigitte Gimenez teaches in St. Vincent's new Bridge program, which caters to redshirted children. She previously taught pre-kindergarten and kindergarten.

"There's nothing magic about the number 5," she said. "All children are gifted. Some just open their packages later than others."

Buffington said redshirting is always beneficial for children who may be unprepared for the next step.

"You can't make a mistake doing that," she said. "You can make a mistake pushing."

No reliable studies have been done on the long-term effects of redshirting. It's difficult to determine how children who were redshirted would have performed if they had entered kindergarten instead.

Based on anecdotal evidence, however, researchers have begun to question the benefits, which Katz believes are short-lived. She has watched her 13-year-old twin grandsons, who were redshirted, struggle socially.

The boys are the oldest in their class. Children who are their age but in the next grade look down on them, she said.

"As kids get older they compare themselves to others of the same age," Katz said. "They seemed to do well academically, but now they are complaining."

According to Katz's research, redshirted students had more behavior problems than their peers. Some may have had special needs or learning disabilities that were not diagnosed; instead they were dismissed as immaturity. Simpson, of the early childhood educators' group, offers his advice: "Be careful."

He said some parents mistake their child's normal anxiety about kindergarten - and perhaps their own anxiety - for a lack of school readiness.

"Children develop at naturally different rates," he said. "Our kindergarten teachers and our school districts need to be prepared with a curriculum that's appropriate for all of those children."