Ministers are concerned that the 11-14 timetable is overloaded and are sensitive to claims that schools are being asked to cover too much ground.
They want to scale back KS3 demands, in part by reducing duplication of material covered in different courses, although they say that all subjects will remain in the curriculum.
The National Union of Teachers said the review did not go far enough and that it was not clear how ministers would reduce the demands on teaching time. Under the review, science, history, geography and design are to receive extra attention. Ministers want to enliven science teaching in particular, with real-life issues given more prominence.
The move follows a detailed critique of KS3 in last month's 14-19 white paper. Despite significant improvements in early secondary teaching recently "the design of the curriculum has some significant problems," said the paper.
It added: "Some programmes of study are less coherent than they could be and some material is repeated in different subjects.
"The amount of prescription leaves schools with little space to timetable catch-up provision for those who are struggling, and to offer really stretching opportunities for those who have particular gifts."
Ministers want all of the existing subjects to remain in the curriculum, but more time spent on catch-up provision and classes for gifted and talented pupils.
They also want more emphasis in science on issues relevant to pupils' daily lives, along the lines of changes to KS4 science, being introduced next September.
The white paper said of the subject: "At present, the curriculum sets out a long shopping list of facts to be learned. "Not only the key conceptual underpinnings of the subject, but also its excitement, relevance and crucial importance are too easily lost."
The white paper's authors believe history and geography are in a similar position. In design and technology, one perceived problem was that pupils were required to complete a large number of tightly-specified tasks.
Changes following the review will be in place by 2008.
John Bangs, NUT head of education, said: "We welcome the fact that there is a review of KS3, but it doesn't go far enough in terms of reducing content."
The KS3 strategy is also being renamed the secondary national strategy, as some of its work is extended to KS4. A new online test in information and communications technology is scheduled for introduction in 2008 - four years after it was first trialled - and included in league tables alongside pupils' maths, English and science results.
Parents are also to be given more information about their children's achievements at 14. A new "pupil profile", setting out youngsters' results in every subject through tests or teacher assessment, will be launched.
Professor Edgar Jenkins, of the Royal Society, welcomed the move to review KS3 science but said any change had to backed by sound evidence, proper funding and support for teachers.