With the return of the university academic year some TV programmes have discussed whether homework matters.
The UK originally had guidelines on the numbers of hours but in 2012 these were scrapped.
DERA digital library from the UCL Institute of Education. has some digitised documents from UK government education bodies about hours of study.
OECD conducts international studies which focus on areas like hours of study and achievement.
In the book Low-Performing Students: Why They Fall Behind and How To Help Them Succeed there is an interesting graph on hours spent doing homework and low performance. This is discussed further in this blog post.
In general it finds The PISA figures show that on average across OECD countries, for each hour per week students spend doing homework, they score 4.5 points higher in reading and mathematics and 4.3 points higher in science. However concerns have been raised that homework perpetuates socio-economic inequality as the amount set is usually related to what type of school and background the children have.