Our research objectives focussed on monitoring (i) students' activities during experimental teaching phases in an out-of-school gene technology lab; (ii) potential relationships with variables such as work group size and cognitive achievement. Altogether, we videotaped 20 work groups of A-level 12th graders (N = 67) by continuous recording of their lab-work phases. Subsequent analysis revealed nine categories characterizing the students' most relevant activities. Intra- and inter-observer objectivity as well as reliability scores confirmed the good fit of this categorization. Based on the individual time budgets generated, we extracted four clusters derived from students' prevalent activities. A cross-tabulation of two cluster analysis methods independently used showed a high level of agreement. Clusters were labelled as (i) 'all-rounders' (members of which applied similar portions of time to the main activities), (ii) 'observers' (members' dominating activity focussed on in-group observation of the lab-work), (iii) 'high-experimenters' (members predominantly engaged in specific hands-on activities), and (iv) 'passive students' (members mainly engaged in activities with no experimental relation). Particularly, we found members of clusters 1 and 2 in four-person work groups while members of clusters 3 and 4 were prevalent in three-person groups. During the educational intervention, students of all clusters improved their cognitive achievement on a short-term and a long-term schedule. However, only the 'all-rounders' revealed a high level of persistent (long-term) knowledge with no decrease rate at all. We draw conclusions with respect to work group sizes as well as to organisational aspects of experimental lessons.
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