Since 1970, the high school graduation rate for 17-year-olds has remained flat
During the first half of the 20th century, the high-school graduation rate of 17-year-olds increased significantly. In the last 40 years, however, that rate has remained about the same. Today, just over three-quarters of 17-year-olds graduate from high school.
High school graduates as a proportion of the age-17 population
Source: U.S. Department of Education, Digest of Education Statistics, 2011.