School history exams have "serious flaws" and risk penalising the brightest pupils, a government-funded report says.
Courses ignore long periods of history, the study says
The Historical Association recommends a "complete overhaul" of teaching of the subject at GCSE and A-level.
Much of the curriculum is speculative and unhistorical, its report adds.
In one exam, pupils were asked what ancient Romans would have made of a 19th-Century cartoon about the quality of London's drinking water.
"To take such an unhistorical approach to chronology breaks some of the rules of the discipline," report author Sean Lang said.
He found that while history teaching was generally very good, there were "serious flaws" with A-level and GCSE courses and test papers.
Mr Lang said exams were "regularly" found to reward speculation and unhistorical thinking.
"There is a danger that accurate answers can be penalised. If that does happen we would be very concerned indeed," he added.
Courses often focused on Hitler and Henry VIII and ignored areas like the British Empire and even the Holocaust, Mr Lang said.
He added: "The subject as it is assessed is beginning to part company with the subject itself. The people who suffer are the pupils."
The report argues that all children should have a "historical education" up to the age of 16, which could include making greater use of history in citizenship lessons.
But it stopped short of calling for history to be made compulsory beyond the age of 14 - when many pupils choose to drop it.
The Historical Association's review of history in secondary schools was part-funded by the Department for Education and Skills.