Spending one hour per week on homework is associated with a 15% reduction in the probability of scoring poorly in mathematics, compared to doing no homework. Devoting two hours per week on homework is associated with a 36% reduction in that likelihood, and three hours per week is associated with a 50% reduction. The probability of scoring poorly continues to decrease as the number of hours spent on homework increases, but only up to a point, after which there are nil returns on the investment (OECD, 2016c). They can include the lack of a suitable, quiet place at home to study, the need to contribute to family and other activities, inadequate parental guidance or supervision in students' younger years, lack of confidence in their ability to understand or complete the homework, and lack of interest in the task and/or subject matter.