Primary school children are spending more time on English and maths and less on other subjects, a study suggests.
More time is given to numeracy
Researchers identified a steady rise in time spent on the three Rs by juniors in England over the six years to 2002.
Time spent on most other subjects - particularly history and geography - fell over the same period, said a report for the QCA curriculum watchdog.
The changes accompanied the start of national strategies to boost performance in literacy and numeracy.
Standards in those areas rose, as judged by the national tests, although the improvement has now reached a plateau.
For this study, a team from Manchester University analysed time spent on different subjects by a sample of 1,000 schools in England between 1997 and 2002.
They found the percentage spent on English rose from 26.6 to 29.2 for children aged from seven to 11.
Time spent on maths rose from 19.8% to 22%.
Over the same period, time spent on science fell from 10.1% to 8.5%.
The share of time given to history and geography fell from 4.8% to 3.7%.
Earlier this year, the chief inspector of schools in England, David Bell, said a "two-tier" curriculum was developing, where teaching in maths and English was better than that of other subjects.
Martin Roberts, of the Historical Association, said subjects such as history and geography were vital parts of children's education.
"The squeeze on humanities has been going on for about 10 years now and this can't be anything but damaging," he said.
"Children need to be literate and numerate but if they are going to be healthy citizens of society they need to know about history, geography and English literature."
The government does not set out how much time should be spent on each subject in primary schools.
But one hour of English and a maths lesson each day is suggested under its literacy and numeracy schemes.
The Historical Association and the Geographical Association are working on the idea of linking history, geography and citizenship as a subject for GCSE.