WASHINGTON >> America’s teens are using more marijuana and less alcohol, according to an annual government study of eighth-, 10th- and 12th-graders across the country.

Some 6.1 percent of high-school seniors reported using marijuana this year, up from 5.2 percent in 2009, according to the Monitoring the Future survey released by the National Institutes of Health.

Marijuana use by 10th-graders climbed from 2.8 percent to 3.3 percent, and for eighth-grade students it edged up from 1.0 percent to 1.2 percent.

“These high rates of marijuana use during the teen and preteen years, when the brain continues to develop, place our young people at particular risk,” said Dr. Nora D. Volkow, director of the National Institute on Drug Abuse.

On the other hand, binge drinking is on the decline. While 23.2 percent of high school seniors reported having five or more drinks in a row, that’s down from 25.2 percent a year earlier. The binge rate for this age group peaked at 31.5 percent in 1998.

On other topics the survey found:

>> Use of ecstasy, which had declined in the early 2000s, is on the increase again.

>> There was a small increase in teens injecting heroin, but only among 12th-graders.

>> Use of cocaine remained low after declining from levels in the 1980s and 1990s.

The survey conducted by the University of Michigan covered 46,482 students in 396 schools.