As part of the new national curriculum being developed and rolled out across Australian schools, sex education will become standardised into a health and physical education stream.

Under the proposed new curriculum, which is still being developed, children in grades 3 and 4 will learn ''the appropriate knowledge, understanding and skills to manage the physical, emotional and social changes they will experience as they reach puberty''.

Children will also be encouraged to develop ''appropriate ways'' to respond to diversity that ''demonstrate respect and value difference''.

Liberal senator Brett Mason expressed alarm at the proposal, questioning whether children in grades 3 and 4 should be taught about sexual health.

''There are quite a few people who find that just a bit young,'' Senator Mason said. ''I can understand why some parents would find that slightly … premature.''

In grades 5 and 6, children will be taught in greater detail about the emotional, physical and hormonal changes associated with puberty.

Children in years 7 and 8 will be taught ''self-management strategies'' to help them navigate the changes they are experiencing, including how to recognise sexual feelings and to ''evaluate behavioural expectations'' for different social situations.

''Students need to develop the knowledge, understanding and skills to recognise instances of discrimination and harassment and act responsibly to support their own rights and feelings and those of others,'' the guidelines state.

Senator Mason said he was not a parent but still questioned whether it was appropriate to be taught about ''sexual feelings'' by years 7 and 8.

But Robert Randall, acting chief executive of the Australian Curriculum, Assessment and Reporting Authority, said many children were already experiencing puberty by grades 5 and 6, and it was appropriate they be given information and support to help them understand what they were going through.

He said children were already taught differing forms of sex education in New South Wales from grades 3 and 4, and in Victoria from grades 5 and 6.

A spokeswoman for School Education Minister Peter Garrett said a ''shaping paper'' for the new curriculum would be put out for public comment in February.