All-day schools in Switzerland have been discussed as a possible means to promote school achievement and to reduce correspondent disparities based on socioeconomic status or first language. This contribution explores those assumptions based on a sample of 1806 students from 53 open all-day schools located in the German-speaking part of Switzerland, which have been examined as part of a longitudinal study between the end of first and the end of second grade, with some students continuously utilizing all-day school offerings while others did not. Continuous utilization of all-day school offerings did not affect the development of mathematical skills, regardless of the quality of all-day school offerings. At the end of first grade, social and cultural disparities were found, with a higher socioeconomic status and German/Swiss-German as first language being linked to higher mathematical skills. Continuous utilization of all-day school offerings reduced disparities based on socioeconomic status. With regard to first language, opposite results emerged, with continuous utilization resulting in increased disparities.

Keywords
All-day school, Extended education, First language, Mathematical skills, Socioeconomic status