High school diplomas in the United States need to have much more rigorous standards if they are to have any future credibility, says a report.
US high school diplomas have been accused of losing their value
As English school exams face a shake-up this week, there is also scrutiny of school-leaver qualifications in the US.
The English exam system is expected to adopt a new diploma structure - but the study by the American Diploma Project is critical of the US version.
It says it is often "little more than a certificate of attendance".
The two-year investigation, carried out by an alliance of education groups and specialists, has concluded that the high school diploma is a "broken promise" in need of comprehensive change.
"The diploma has lost its value because what it takes to earn one is disconnected from what it takes for graduates to compete successfully beyond high school - either in the classroom or in the workplace," says the report.
It concludes that standards in English and maths need to be tougher if the qualification is to be useful for employers or higher education - and that in most states pupils are not taking difficult enough courses.
The United States does not have a national education system - and this report will be seen as pushing towards more national standards, with exams becoming more of a "common currency".
Graduating with a high school diploma should mean that the pupil has achieved an appropriate standard in a range of core and specialist subjects.
But in a damning conclusion it says the diploma "often serves as little more than a certificate of attendance".
The project says that the lack of adequate benchmarked standards means that more than half of students entering higher education courses need to have remedial lessons in either maths or English.
It also reports that employers are dissatisfied with students' literacy and numeracy skills.
The report recommends that there should be much clearer common standards and assessment, so that a school-leaving qualification will be able to represent pupils' abilities.
The US Secretary of Education, Rod Paige, applauded the project and said the report "underscores the need for high school reform".
Teachers' representatives were not all impressed by the harsh conclusions, with some saying pupils and staff were working hard and rejecting the claim that the diploma had lost its value.
The future direction of England's secondary school exam system is going to be outlined on Tuesday, in a report from former chief schools inspector Mike Tomlinson.
It is expected to propose that A-levels and GCSEs be incorporated within a diploma structure.