Educators and psychologists have long feared that children entering school with behavior problems were doomed to fall behind in the upper grades. But two new studies suggest that those fears are exaggerated.

One concluded that kindergartners who are identified as troubled do as well academically as their peers in elementary school. The other study found that children with attention deficit disorders suffer primarily from a delay in brain development, not from a deficit or flaw.

Experts say the findings of the two studies, being published today in separate journals, could change the way scientists, teachers and parents understand and manage children who are disruptive or emotionally withdrawn in the early years of school. The studies might even prompt a reassessment of the possible causes of disruptive behavior in some children.

'Landmark findings'

"I think these may become landmark findings, forcing us to ask whether these acting-out kinds of problems are secondary to the inappropriate maturity expectations that some educators place on young children as soon as they enter classrooms," said Sharon Landesman Ramey, director of the Georgetown University Center on Health and Education, who was not connected with either study.

In one study, an international team of researchers analyzed measures of social and intellectual development from more than 16,000 children and found that disruptive or anti-social behaviors in kindergarten did not correlate with academic success at the end of elementary school.

Kindergartners who interrupted the teacher, defied instructions and picked fights were performing as well in reading and math as well-behaved children of the same abilities when they reached fifth grade, the study found.

Other researchers cautioned that the findings, reported in the journal Developmental Psychology, did not imply that emotional problems were trivial or could not derail academic success in the years before or after elementary school.

In the other study, researchers from the National Institute of Mental Health and McGill University, using imaging techniques, found that the brains of children with attention-deficit hyperactivity disorder developed normally but more slowly in some areas than the brains of children without the disorder.

The disorder, also known as ADHD, is by far the most common psychiatric diagnosis given to disruptive young children; 3 percent to 5 percent of school-age children are thought to be affected. Researchers have debated whether it was because of a brain deficit or a delay in development.

Doctors said the report, published in the Proceedings of the National Academy of Sciences, helps explain why many children grow out of the diagnosis in middle school or later.

The findings in the first study grew out of a collaboration among a dozen researchers to reassess data from six large child-development studies performed since 1970. Each of the six studies tracked hundreds of children from an early age through elementary school on a number of measures.

The researchers adjusted the findings to eliminate the influence of family income and family structure.

Studies' results

While there was little correlation between behavior problems in kindergarten and later academic success, the researchers found scores on math tests at ages 5 or 6 were highly correlated with academic success in fifth grade. Kindergarten reading skills and scores on attention measures - where youngsters with ADHD falter - also predicted later academic success, but less strongly than math scores did. The pattern was about the same in girls as in boys, and for children from affluent families as well as those from lower-income groups.

In the second study, government psychiatric researchers compared brain scans from two groups of children: one with attention deficit disorder, the other without. The scientists had tracked the children - 223 in each group - from ages 6 to 16, taking multiple scans on each child.

In a normally developing brain, the cerebral cortex - the outer wrapping, where circuits involved in conscious thought are concentrated - thickens during early childhood. It then reverses course and thins out, losing neurons as the brain matures. The study found that, on average, the brains of children with ADHD began this "pruning" process at age 10 1/2, three years later than their peers.