Given the rapid development of modern biotechnology, attention to socioscientific issues in educational contexts is crucially important to support students in becoming responsible citizens. The authors' research focused on the impact of discussing socioscientific issues during biology lessons under 3 different treatments (teacher guided, student centered, text only), comparing these treatments with regard to cognitive achievement, cognitive load, and instructional efficiency. The biology lessons were part of an educational intervention with Bavarian 10th-grade students (N = 583) in an out-of-school laboratory on plant genetic engineering. The teacher-guided group performed significantly better regarding knowledge increase, while the cognitive load of the student-centered group was significantly higher. Accordingly, teacher-guided discussion led to the highest instructional efficiency, suggesting an enhanced cognitive achievement through the teacher's guidance. However, a student-centered approach allows students to contribute more of their own opinions, making further research in this area desirable. Finally, we discuss potential implications for teaching and teacher education.