But it adds: “Schools may, however, choose to spread their teaching of the key stage 1 national curriculum over a longer period and thus cover aspects of key stage 1 with children in reception classes if they judge this appropriate to the needs and stage of development of the children.”

The guidance will help primary teachers decide when to start teaching the national curriculum to five-year-olds, says SCAA, which launched a series of conferences for primary school teachers this week on how to plan the curriculum for five to 11-year-old children.

Also, a 48-page booklet, Planning The Curriculum at Key Stages 1 and 2, will go out to schools later this month. Judith Morris, SCAA’s assistant chief executive with responsibility for key stage 1, hopes the booklet will clear up some of the confusion over when schools start teaching the national curriculum to young children. Some heads were unclear about whether all nine subjects had to be taught from five, she said.

But the guidance states: “Schools have some discretion over when to start teaching the key stage 1 programmes of study, as the law requires only that programmes of study should be taught during the key stage, not that they should be introduced at a particular time.”

SCAA has clarified this point with the Department for Education and the Office for Standards in Education so that all three organisations give out the same advice.

However, the suggestion that the national curriculum can be extended to children in reception classes will annoy many early-years experts.

Vicky Hurst, lecturer in early childhood at Goldsmiths’ College and vice-president of the National Campaign for Nursery Education, said few teachers were trained to teach the under-fives and were not in a position to judge whether aspects of the national curriculum are appropriate to their needs and stage of development.

She complimented SCAA for making it clear that the starting date for the national curriculum was flexible for five-year-olds, but said: “There is a world-famous curriculum for education under five which goes on in state nursery education. It is appropriate to their ways of learning and involves playing and exploring. It lays foundations for the national curriculum at a later stage. ”

SCAA, which has conducted an unofficial pilot of the planning guidance in about 30 schools nationwide, hopes the booklet and the conferences in London, Manchester and Bristol will help teachers to interpret the new Dearing national curriculum.

The guidance, which primary teachers have requested, makes suggestions about how to establish curriculum balance and progression. It also proposes ways to allocate time for different subjects and aspects of subjects through topic work and individual subject teaching, looking at different types of schools.

For instance, an infant school with a high intake of children for whom English is not their first language is shown allocating 32 per cent of curriculum time for English; in another infant school, the allocation is 23.5 per cent.

It also shows, for example, how a cross-curricular project on fast food, carefully planned to cover particular aspects of geography and maths, could be set up with notional time allocations of seven hours each for maths and geography and two hours for information technology.

Chris Jones, SCAA assistant chief executive for key stage 2, said of the guidance: “Had it been written five years ago it would have been contentious. Some primary teachers will say it is outside their culture - things take as long as they need to take. But the message we give here is hard-nosed. We say you cannot do the job if you think like that.”

Judith Morris said: “Unless you use curriculum time properly, the curriculum timetable just fills up by default.”

Since the implementation of the national curriculum in primary schools, teachers and Government advisers have been debating the pros and cons of topic teaching, which can cover several subjects at once, versus subject teaching. But SCAA says the new booklet makes no comment on that debate.