The Program for International Student Assessment (PISA) by the OECD measures student study time during formal school periods and during periods of out-of-school-time (OST). The purpose of these items is to account for differences in country to country achievement levels. However, analyses of the impact of additional study time on student achievement have produced conflicting results across countries. While more time given to a school subject within formal school is positively related to achievement in that topic, more time spent on OST is negatively related to average achievement between and within countries. The paper proposes a reconceptualization of OST and achievement by integrating theoretical frameworks of study time, student abilities, and student feelings of efficacy. The results of a descriptive and conceptual analysis of a set of new survey items in the 2015 PISA for 22 countries shows that students benefit from additional study time by having increased feelings of efficacy in a school subject (such as science) but not in measurable levels of achievement. While country to country levels OST participation rates are different, the patterns of relationships between OST participation, student achievement, and attitudes are similar.