(AP) – U.S. students don't know much about American history, according to results of a national test released Tuesday. Just 13 percent of high school seniors who took the 2010 National Assessment of Educational Progress, called the Nation’s Report Card, showed solid academic performance in American history.The two other grades didn't perform much better, which just 22 percent of fourth-grade students and 18 percent of eighth-graders scoring proficient or better.The test quizzed students on topics including colonization, the American Revolution and the Civil War, and the contemporary United States. For example, one question asked fourth-graders to name an important result of the U.S. building canals in the 1800s.