This paper investigates the effect of primary school students' utilization of extended education offerings and of the quality of extended education on reading achievement in the German-speaking part of Switzerland. All-day schools are being set up. Among other reasons, as a means to level the increasing scholastic demands in the primary schools. In this context, it is expected that students' utilization of extended education will have a positive impact on their reading achievement. The authors analyzed data on 1,002 students from the longitudinal 'EduCare-TaSe: All-Day School and School Success?' study. Extended education offerings did not have a general effect on reading achievement. There was also no compensatory effect regarding the language spoken at home or socioeconomic status. However, the quality of extended education offerings had a positive effect on reading achievement in students with long-term utilization of extended education offerings. (DIPF/Orig.)