Ask a parent whether homework helps and you’ll get a confident answer either way. Ask the researchers who’ve actually measured it, and the honest answer is: it depends — mostly on how old the child is.

The Study Everyone Cites

Nearly every argument about homework, on either side, eventually traces back to one body of work: a synthesis led by Harris Cooper, a psychology professor at Duke University, along with Jorgianne Civey Robinson and Erika A. Patall, published in the journal Review of Educational Research in 2006. The team reviewed more than 60 studies on homework conducted between 1987 and 2003, making it the most comprehensive analysis of the question available even two decades later.

The headline finding was a positive but modest correlation between homework and achievement overall — but that average conceals real variation by age. In studies measuring a simple correlation between homework and test scores, the relationship was close to zero in elementary school, rose to r = .07 in middle school, and reached r = .25 in high school — a meaningfully stronger relationship, though still moderate by statistical convention. In the smaller set of studies that experimentally assigned homework rather than just observing it, the effect was considerably larger: a weighted average effect size of d = .60 across all such studies, and d = .53 in the subset using true random assignment.

Age Changes Everything

Cooper’s team also examined why younger kids seem to benefit less. Younger children are more easily derailed by distractions at home, haven’t yet developed effective independent study strategies, and may be getting more out of homework’s side effects — practicing time management and self-discipline — than out of the academic content itself. For elementary-aged kids, the research suggests homework’s real value may be less about mastering material and more about building habits that make studying possible later.

That developmental view is why Cooper has resisted both ends of the debate. “Kids burn out,” he has said. “The bottom line really is all kids should be doing homework, but the amount and type should vary according to their developmental level and home circumstances.” He has also used a memorable analogy for dosage, comparing homework to medication: “If you take too little, they’ll have no effect. If you take too much, they can kill you. If you take the right amount, you’ll get better.”

The 10-Minute Rule, and Its Limits

That dosage question is where the widely cited “10-minute rule” comes from — the guideline, endorsed by the National PTA and the National Education Association, that students should get about 10 minutes of homework per grade level per night: roughly 40 minutes in fourth grade, about two hours by senior year of high school. Cooper has pointed to it as a reasonable rule of thumb rather than a rigid formula. His own data support the idea that returns taper off well below what some heavy homework loads assign — additional homework beyond roughly two hours a night showed no further association with achievement, even for older students.

Not every researcher accepts that the correlation proves homework is driving the improvement in the first place. Cathy Vatterott, an education professor who has written extensively on the subject, has pushed back on causal claims: “Does homework cause achievement, or do high achievers do more homework?” Students who are already succeeding may simply be the ones most likely to complete assigned work, which would inflate the apparent benefit without homework actually causing it. Vatterott has argued for scaling back or eliminating homework for the youngest students specifically because the evidence of benefit at that age is thin.

What Newer Research Adds

More recent work has tried to move past overall correlations toward what specific kinds of homework actually do. A 2024 systematic review in Campbell Systematic Reviews, led by Liping Guo and colleagues, focused specifically on experimental studies and found an overall effect size of 0.45 for students who completed assigned homework versus those who didn’t — with the strongest benefits concentrated in arithmetic computation and problem-solving. The same review found that, in head-to-head comparisons, moderate homework loads of 20 to 30 minutes outperformed shorter 10-to-15-minute assignments for building conceptual understanding — but the authors were explicit that they still could not identify a single optimal dose, and called for more rigorous research, particularly for secondary students.

Taken together, the research doesn’t support either “homework doesn’t work” or “more homework is always better.” It supports something less quotable: that homework’s payoff depends heavily on age, is easy to over-dose past a fairly low ceiling, and that nobody has yet nailed down the precise amount that works best for any given subject or grade — which may be exactly why the debate keeps being fought in absolutes instead.

Sources: Harris Cooper, Jorgianne Civey Robinson, Erika A. Patall, “Does Homework Improve Academic Achievement? A Synthesis of Research, 1987-2003,” Review of Educational Research, Spring 2006 (assess.ucr.edu); “Homework: Is It Good for Kids? Here’s What the Research Says,” Time, August 2016 (time.com); “Is Homework Getting Too Complicated? A Look at How Homework Policies Are Changing,” Duke Today, March 2006 (today.duke.edu); Liping Guo et al., “The Relationship between Homework Time and Academic Performance among K-12: A Systematic Review,” Campbell Systematic Reviews, September 2024 (doaj.org).