CHILDREN are being lumbered with hours of homework every week - but the extra slog doesn't do them any good.

Research reveals primary school homework offers no real benefit - and only limited results in junior high school.

Only senior students in Years 11 and 12 benefit from after-school work, associate professor Richard Walker said.

"What the research shows is that, in countries where they spend more time on homework, the achievement results are lower," Dr Walker, from Sydney University's Education Faculty, said.

"The amount of homework is a really critical issue for kids. If they are overloaded they are not going to be happy and not going to enjoy it. There are other things kids want to do that are very valuable things for them to be doing.

"I don't think anyone except senior high school students should be doing a couple of hours of homework.

"At the moment homework (is often) an add-on because parents want it."

NSW public schools each set their own homework policy after consultation with teachers and parents.

Teachers are advised to keep homework levels low in primary school but are permitted to increase the study load by Year 7. Data from the Australian Institute of Family Studies (AIFS) found 95 per cent of 10 and 11-year-old students are given homework.

Dr Ben Edwards, manager of the AIFS's study of 10,000 children, said a small portion of children did more than seven hours homework a week but that could be attributed to extracurricular studies such as music classes.

While the majority of 10 and 11-year-olds - 59 per cent - do less than two hours of homework per week, 22 per cent do three or four hours a week. Five per cent do seven or more hours a week.

It's not only kids who get tied down with homework - parents are also heavily involved. Dr Edwards said almost half of mums and dads - 41 per cent - helped out three or four days a week, with 15 per cent also chipping in on five or more days.

"A little bit of homework is probably OK at all ages, if part of the reason is to help kids become self-directed learners," Dr Walker said.

"But what the research shows is that only happens when upper primary and middle school students are given some assistance.

"If we (ask) if homework benefits outcomes, then it is pretty clear it does not at primary school and has pretty limited benefits in junior high school and some benefits in high school from Years 11-12."

Originally published as The real truth on homework