Imagine a kindergarten classroom. Picture the vividly colored scalloped borders on the walls, the dancing letters, maybe some charming cartoon barnyard animals holding up “Welcome to School!” signs.

That bright, cheery look has become a familiar sight in classrooms across the country, one that has only grown over the last few decades, fed by the proliferation of educational supply stores. But to what effect?

new study looked at whether such classrooms encourage, or actually distract from, learning. The study, one of the first to examine how the look of these walls affects young students, found that when kindergartners were taught in a highly decorated classroom, they were more distracted, their gazes more likely to wander off task, and their test scores lower than when they were taught in a room that was comparatively spartan.

The researchers, from Carnegie Mellon University, did not conclude that kindergartners, who spend most of the day in one room, should be taught in an austere environment. But they urged educators to establish standards.

“So many things affect academic outcomes that are not under our control,” said Anna V. Fisher, an associate professor of psychology at Carnegie Mellon and the lead author of the study, which was published in Psychological Science. “But the classroom’s visual environment is under the direct control of the teachers. They’re trying their best in the absence of empirically validated guidelines.”

In the early years of school, children must learn to direct their attention and concentrate on a task. As they grow older, their focus improves. Sixth graders, for example, can tune out extraneous stimuli far more readily than preschoolers, the study’s authors noted.

But could information-dense kindergarten classroom walls, intended to inspire children, instead be overwhelming? Could all that elaborate décor impede learning? Some experts think so.

“I want to throw myself over those scalloped borders and cute cartoon stuff and scream to teachers, ‘Don’t buy this, it’s visually damaging for children!’ ” said Patricia Tarr, an associate professor at the University of Calgary who researches early childhood education and art education, and was not involved in the study.

Dr. Tarr has long railed against the notion of “decorating” a classroom. In a 2004 paper called “Consider the Walls,” published in Young Children, the journal for the National Association for the Education of Young Children, she argued that classrooms could become so cluttered with commercial posters and mobiles that they obscured the children’s own drawings and writings, posing special challenges to any child with attention deficits.

For the new study, 24 kindergartners were taught in two classroom settings: one unadorned, the other festooned with commercial materials like posters and maps, as well as the children’s artwork. The children sat on carpet squares in a semicircle facing the teacher, who read aloud from a picture book. They took six five- to seven-minute science lessons over two weeks on topics such as plate tectonics, the solar system and bugs. After each lesson, the children took multiple-choice picture tests. The lessons were videotaped, to monitor how often the children’s gazes wandered.

In the austere classroom, the kindergartners — age-appropriately wriggly and restless — were inclined to be distracted by others, or even themselves. But in the decorated one, the visuals competed with the teacher for their attention. The children spent far more time off-task in the decorated classroom than in the plain one, and their test scores were also lower.

The researchers acknowledged that their study looked only at one small group of kindergartners, and that its results may not apply to older children. Moreover, the students sat in the rooms for one lesson at a time, rather than a full school day.

The next step, said Sara E. Rimm-Kaufman, an educational psychologist at the University of Virginia who was not involved in the study, would be to replicate the same experiment, but in classrooms where children spent the entire day.

She noted that relatively little had been written about how to make effective use of classroom walls. But she said that if young children were “seeing so much at once, they cannot independently differentiate what is important; they may tune out the teacher.”

Yet teachers sometimes feel compelled to make those walls attractive, she said, “because they know parents are coming to an open house night, and parents expect to see a decorated classroom.”

Some educators have resisted the trend toward the ever-more embellished classroom. Montessori schools have long emphasized a calmer, understated look. Individual teachers have eschewed the pricey trend, too.

“We used to paper our walls from floor to ceiling, covering them 100 percent,” said Ingrid Boydston, a kindergarten teacher at Bridgeport Elementary School in Santa Clarita, Calif.

Now Mrs. Boydston, a California teacher of the year in 1999, encourages teachers to let wall displays grow from the children’s experiences. She sees educational value in deliberately leaving areas blank under signs that might say “Watch This Space!” For a recent lesson about the artist Monet, she stood in front of a white board, wearing a wide-brimmed straw hat and smock and speaking in a French accent. Afterward, she filled the board with key words that her 27 young students remembered from her talk. Then the children went to the room’s paint center, where they went to work with cotton swabs.

Finally, it was time to adorn a blank wall. Mrs. Boydston filled it with artwork: the children’s Monets, not Claude’s.