J.D. Tuccille considers the effects of having too much work outside the classroom:
A study, published last year in the Journal of Experimental Education, takes a dim view of the heavy workloads under which high school kids in “10 high-performing high schools in upper-middle-class communities” stagger. Results indicated that students in these schools average more than three hours of homework per night. Students who did more hours of homework experienced greater behavioral engagement in school but also more academic stress, physical health problems, and lack of balance in their lives. Which is to say, even if you think that homework can be a good thing, there’s a limit. More is not better, say researchers from Stanford University, Lewis and Clark College, and Villanova University.
Granted, those “upper-middle-class communities” may not be the most broadly representative; the average American high schooler spends about an hour and a half on homework per day. But as Misty Adoniou points out, even modest amounts of homework may widen achievement gaps:
Research finds that homework doesn’t improve learning outcomes in primary school, and has a weak link to improved outcomes in junior high school. Those improvements are connected to parental involvement – but parents who are keen supporters of homework may be disappointed to hear that their positive contribution is largely just ensuring their children hand in their homework. …
There are many parents, dedicated and desperately interested in their children’s education, who cannot involve themselves in their children’s homework. They may not have had schooling opportunities themselves, they may speak English as an additional language, they may work long hours or shifts, or they may just be like most of us, and simply can’t remember what a quadratic equation is. Those with spare cash buy the homework support, in the form of after hours tutoring. In high school, where homework tasks contribute substantially to the course grade, homework is the great unequalizer.