As the summer winds to an end and the school bell tolls, an article extolling the virtues of play and relaxation seems timely. Writing in the journal Pediatrics, a group of researchers from Albert Einstein College of Medicine in New York showed that, compared to those who have minimal or no recess time, elementary school children who have free time during the day receive higher ratings from teachers on their classroom behavior.

This makes intuitive sense. And a few small studies have demonstrated the value of recess—defined as a break in the school day that is given over to free, unstructured, active play. This prior research showed that children are less fidgety and more attentive after recess. In a communiqué from the American Academy of Pediatrics (AAP) in early 2007, Dr. Kenneth Ginsburg, a pediatrician at the University of Pennsylvania, described play as essential for healthy brain development, with positive effects for intellectual and emotional development. It promotes not just intelligence, but also creativity, imagination, and resilience.

The power of this study comes from its size and breadth. The authors used a data set from a large survey sponsored by the U.S. Department of Education. They reviewed data collected on more than 15,000 students, 8 or 9 years old, most of whom were third graders. Students came from all major ethnic groups and every geographical region in the United States. The study included an equal number of boys and girls, who attended both public and private schools. Parents ranged in education from those who had not finished high school to those who had earned a graduate degree. All socioeconomic levels were represented, as were communities ranging from urban to rural.

One of the study's most surprising findings was the appalling state of recess in the United States. Three in ten children have either no recess or only enjoy a minimal break during the day (less than 15 minutes). Children who are black or Hispanic are more likely to be deprived of recess, as are children who come from lower income families, have parents with less education, or are living in larger cities and in the South.

The authors also explain that children have less free play or unstructured time in school now than they did in the 1960s or 1970s. They theorize that this is a response to the No Child Left Behind Act of 2001. To meet the demands of the law, which requires schools to improve test scores in reading and math, administrators have cut back on recess, arts programs, and physical education.

Paradoxically, the reduction in unstructured time for students may not be achieving its aims. Students who are kept in classrooms all day without a break are likely to be less attentive and may also learn less efficiently.

Moreover, the negative consequences of such a reduction in recess are not limited to intellectual or emotional development. The rate of obesity in children has tripled over the last few decades. On its own, recess time can't reverse this trend, but it can contribute to promoting the habit of an active lifestyle.

The study did not provide evidence for how much recess is optimal. Researchers working in this area recognize that children are under numerous competitive pressures in school. As a group, they advocate finding a balance between free time and structured, formal teaching, although more research is needed to determine what a reasonable balance should be.

But the AAP recommends that play, particularly active and creative play (as opposed to sitting in front of a television or computer screen) will help children be more successful. It may even help them learn a few of the social skills they'll need to meet the challenges ahead of them.