The Drei-Länder-Studie (DLS) by Helmut Fend is a school achievement study carried out in 1978/79 on behalf of the Ministries of Education of Hessen, North Rhine-Westphalia and Lower Saxony. The original aim of the study was to compare comprehensive schools with schools of the traditional school system. The present technical report documents the survey instruments of a newly prepared data set, which comprises the assessment and testing of pupils from grade 9 and their teachers. This data set enables more in-depth analyses of school and teaching quality, taking into account the social and performance-related composition of pupils at school and class level (heterogeneity) as well as teaching and learning related attitudes of teachers. The survey focused on data on instruction in English and mathematics, including corresponding subject-specific performance tests, different attitudes of teachers, class and school climate, and social background characteristics of pupils, their achievement anxieties, attributions and aspirations, and parental support.