"We were very pleased to see that," said the study's lead author, Nancy Bener of the Centers for Disease Control and Prevention.
Still, a quarter have at least one soda each day. And when other sugary drinks like Gatorade are also counted, the figure is closer to two-thirds of high school students drinking a sweetened beverage every day.
That's less than in the past. In the 1990s and early 2000s, more than three-quarters of teens were having a sugary drink each day, according to earlier research.
The CDC reported the figures Thursday, based on a national survey last year of more than 11,000 high school students. They appear in one of the federal agency's publications, Morbidity and Mortality Weekly Report.
Consumption of sugary drinks is considered a big public health problem, and has been linked to the U.S. explosion in childhood obesity. One study of Massachusetts schoolchildren found that for each additional sweet drink per day, the odds of obesity increased 60 percent.
As a result, many schools have stopped selling soda or artificial juice to students.
Indeed, CDC data suggests that the proportion of teens who drink soda each day dropped from 29 percent in 2009 to 24 percent in 2010, at least partly as a result.
"It looks like total consumption is going down," said Kelly Brownell, director of Yale University's Rudd Center for Food Policy and Obesity.
But the results of the new CDC study are still a bit depressing, said Brownell, who has advocated for higher taxes on sodas.
"These beverages are the kinds of things that should be consumed once in a while as treat — not every day," he said. "That's a lot of calories."
A 20-ounce Coke, for example, has 240 calories.
Brownell also said it's possible more than a quarter of teens are drinking soda, because many people underreport things they know they shouldn't be eating or drinking.
Bener agreed it's difficult to know if consumption of sugary drinks has been falling much, adding that schools are only half the battle.
"Getting them out of the schools doesn't solve the problem completely because a lot of these drinks are consumed in the home," said Bener, a CDC health scientist.
More detail: About 16 percent have a sweetened sports drink every day, and 17 percent drink some other sugary beverages like lemonade, sweetened tea and flavored milk. Black students were more likely than whites or Hispanics to drink sugary beverages.
The study also found that 7 percent of high school students drink diet soda each day, 5 percent have energy drinks and 15 percent have at least one coffee or tea.
Also, 72 percent drink a serving of water daily, 42 percent drink at least one glass of milk and 30 percent have 100 percent fruit juice.