A law adopting statewide high school exams for graduation took effect in Pennsylvania on Saturday, with the goal of ensuring that students leaving high school are prepared for college and the workplace. But critics say the requirement has been so watered down that it is unlikely to have major impact.

The situation in Pennsylvania mirrors what has happened in many of the 26 states that have adopted high school exit exams. As deadlines approached for schools to start making passage of the exams a requirement for graduation, and practice tests indicated that large numbers of students would fail, many states softened standards, delayed the requirement or added alternative paths to a diploma.

People who have studied the exams, which affect two-thirds of the nation’s public school students, say they often fall short of officials’ ambitious goals.

“The real pattern in states has been that the standards are lowered so much that the exams end up not benefiting students who pass them while still hurting the students who fail them,” said John Robert Warren, an expert on exit exams and a professor of sociology at the University of Minnesota-Twin Cities.