A new report says only about half of all students in the 50 largest U.S. cities graduate from high school.

According to a study released Tuesday by a research center and a group of education advocates, the city with the worst drop-out rate was Detroit in the midwestern state of Michigan, where only one quarter of students graduate from 12th grade.

In New York City and Los Angeles, California about 45 percent of all students receive a high school diploma.

U.S. Secretary of Education, Margaret Spellings, Tuesday called the low graduation rate a "silent epidemic" that is far more likely to affect poor and minority students.

Some information for this report provided by AFP and AP.