This study presents a newly developed test to assess students' knowledge of learning strategies that they use when completing complex assignments at the upper secondary baccalaureate school (Gymnasium) level. The sample included N = 2,300 students at 23 baccalaureate schools in Switzerland and also a small sample of university students (N = 58). We tested hypotheses regarding cognitive, metacognitive, and motivational dimensions of learning. In addition, students' self-reported grades in German were used as an achievement criterion. The analyses included estimation of Cronbach's alpha and distribution of the test scores on the individual and class level. Furthermore, structural equation modeling was carried out. The findings support the reliability and validity of the new test. We found significant differences in terms of gender and school attendance. Learning strategy knowledge showed a positive relationship with student achievement, students' learning motivation, and students'self-reported use of habitual learning strategies.