To improve science learning under demanding conditions, we designed an out-of-school lesson in compliance with cognitive load theory (CLT). We extracted student clusters based on individual effectiveness, and compared instructional efficiency, mental effort, and persistence of learning. The present study analyses students' engagement. 50.0% of our sample ("n" = 250, 5th-8th graders) showed satisfying results, 11.2% were not motivated; 38.8% had difficulties to cope with the learning situation. Presumably, most of them had problems in identifying relevant contents, some were precarious about their capabilities. We suppose that those students may have improved performance with extended active support. We may advance future research on guidance in CLT, and its integration in the field of science education. (Contains 5 tables and 4 figures.)