Achieve Inc. studied the exit tests from six states that volunteered for the review -- Florida, Maryland, Massachusetts, New Jersey, Ohio and Texas.
The states enroll roughly a quarter of all the high school students in the nation and about half the students who are required to pass a graduation exam.
The English tests most closely resemble ACT's EXPLORE test given to eighth and ninth graders, the study said.
In math, students can pass the tests by answering questions that on average fall between the middle of seventh grade and the end of eighth grade, it said.
"We shouldn't lower the bar and we shouldn't put off testing," said Michael Cohen, president of Achieve. "Frankly, it's unfair to the kids. We suggest that states that don't require tests aren't being fair to kids, and are setting them up for a much greater failure later on."