Black students, especially boys, face much harsher discipline in public schools than other students, according to new data from the Department of Education.

Although black students made up only 18 percent of those enrolled in the schools sampled, they accounted for 35 percent of those suspended once, 46 percent of those suspended more than once and 39 percent of all expulsions, according to the Civil Rights Data Collection's 2009-10 statistics from 72,000 schools in 7,000 districts, serving about 85 percent of the nation's students. The data covered students from kindergarten age through high school.

One in 5 black boys and more than 1 in 10 black girls received an out-of-school suspension. Overall, black students were 3½ times as likely to be suspended or expelled than their white peers.

And in districts that reported expulsions under zero-tolerance policies, Hispanic and black students represent 45 percent of the student body, but 56 percent of those expelled under such policies.

''Education is the civil rights of our generation," said Secretary of Education Arne Duncan in a telephone briefing with reporters on Monday. "The undeniable truth is that the everyday education experience for too many students of color violates the principle of equity at the heart of the American promise."

The department began gathering data on civil rights and education in 1968, but the project was suspended by the Bush administration in 2006. It has been reinstated and expanded to examine a broader range of information, including, for the first time, referrals to law enforcement, an area of increasing concern to civil rights advocates who see the emergence of a school-to-prison pipeline for a number of students of color.

According to the schools' reports, more than 70 percent of the students involved in school-related arrests or referred to law enforcement were Hispanic or black.

Black and Hispanic students - particularly those with disabilities - are also disproportionately subject to seclusion or restraints. Students with disabilities make up 12 percent of the student body, but 70 percent of those subject to physical restraints. Black students with disabilities constituted 21 percent of the total, but 44 percent of those with disabilities subject to mechanical restraints, like being strapped down. And while Hispanics made up 21 percent of the students without disabilities, they accounted for 42 percent of those without disabilities who were placed in seclusion.

"Those are extremely dramatic numbers and show the importance of reinstating the civil rights data collection and expanding the categories of information collected," said Deborah J. Vagins, senior legislative counsel at the American Civil Liberties Union's Washington legislative office. "The harsh punishments, especially expulsion under zero tolerance and referrals to law enforcement, show that students of color and those with disabilities are increasingly being pushed out of schools, oftentimes into the criminal justice system."

While the disciplinary data was probably the most startling, the data showed a wide range of other racial and ethnic disparities. For while 55 percent of the high schools with low black and Hispanic enrollment offered calculus, only 29 percent of the high-minority high schools did so - and even in schools offering calculus, Hispanics made up 20 percent of the student body but only 10 percent of those enrolled in calculus.

And while black and Hispanic students made up 44 percent of the students in the survey, they were only 26 percent of the students in gifted and talented programs.

The data also showed that schools with a lot of black and Hispanic students were likely to have relatively inexperienced, and low-paid, teachers. On average, teachers in these schools were paid $2,251 less per year than their colleagues elsewhere. In Philadelphia high schools, though, the discrepancy was more than $14,000.

In recent decades, as more districts and states have adopted zero-tolerance policies, imposing mandatory suspension for a wide range of behavioral misdeeds, more and more students have been sent away from school for at least a few days, an approach that is often questioned as paving the way for students to fall behind and drop out.

A previous study of the federal data from the years before 2006, published in 2010 by the Southern Poverty Law Center, a nonprofit organization, found that suspension rates in the nation's public schools, kindergarten through high school, had nearly doubled from the early 1970s through 2006 - from 3.7 percent of students in 1973 to 6.9 percent in 2006 - in part because of the rise of zero-tolerance school discipline policies.

The data is publicly available at ocrdata.ed.gov.