New data from the U.S. Department of Education shows that 86 percent of Illinois students graduate from high school.  That’s the 20th-highest graduation rate in the country.  The department said Tuesday that the 82.3 percent national graduation rate for the 2013 – 2014 school year was the highest recorded since it started using a new, uniform measure in 2010.  That still leaves nearly 1 in 5 students leaving high school without a diploma.  Education Secretary Arne Duncan praised the improvement but said too many students still drop out.  In Illinois, 90.1 percent of white students graduate.  The numbers are 77.2 percent for black students, 81.3 percent for Hispanic students, 78.5 percent for economically disadvantaged students and 71.8 percent for students with disabilities.  Illinois was above the nation’s numbers in every category.  Iowa’s 90.5 percent overall graduation rate was the country’s highest, while the District of Columbia had the lowest, at 61.4 percent.