With many states crafting assessments based on the common-core standards--and an increasing emphasis on college and career readiness--some are rethinking the kind of tests high school students must pass to graduate, or whether to use such exit exams at all. Twenty-five states, enrolling a total of 34.1 million students, make exit exams a graduation requirement, according to a study released by the Center on Education Policy, a Washington-based think tank. That represents 69 percent of the nation's K-12 enrollment. And that's grown over the past decade: In 2003, 19 states representing 52 percent of U.S. enrollment had such exit exams. But now states including Arizona, Florida, Massachusetts, New Jersey, and Rhode Island plan to use new common-core-aligned tests as exit exams in some form once those tests are fully implemented in 2014-15. Other states are less certain about their plans for the assessments being developed as part of the common-standards push.