Our study focussed on the cognitive achievement potential of low achieving eighth graders, dealing with drug prevention (cannabis). The learning process was guided by a teacher, leading this target group towards a modified learning at workstations which is seen as an appropriate approach for low achievers. We compared this specific open teaching approach with both, a conventional learning at workstations and a traditional teacher-centered approach. Two types of students of lowest stratification level in German school system participated, the regular level (R) and the higher level ones (H). Thus, we compared students of two stratification sub-levels with regard to three teaching methods. Pre-, post- and retention tests were used to monitor knowledge achievement. The modified teaching approach achieved overall best results. R and H students reached similar levels of persistent knowledge in our specific approach. Thus, low achievers could reveal also high cognitive achievements in open learning environments. Consequences for school practice are discussed.