An OECD report on data from the PISA survey looked at homework among 15-year-olds and asked whether homework perpetuates inequalities in education.
According to the report, in 2012 students in the 38 countries covered by the survey spent an average of an hour less on their weekly homework than their predecessors did in 2002 (OECD average 5.9 hours). Socio-economically advantaged students and those who attended socio-economically advantaged schools tended to spend more time doing homework than other students. There was an association between the amount of mathematics homework supplied and the performance of both students and schools, but other factors had a greater effect on overall school performance.
The report concludes that homework provides an opportunity for learning but could reinforce socio-economic differences. Schools and teachers might be able to mitigate the problem by, for example, providing quiet places for study for students with no such facility at home.
Source: Does homework perpetuate inequities in education? (2014) PISA in Focus