Academic language skills and scientific concepts are seen as important factors for school success. The necessity to foster these competencies in preschool particularly applies to children with lower socio-economic status or migrant background. While studies indicate that inquiry-based science education can foster both the development of scientific concepts and academic language, previous research focuses on either science or language outcomes. In a quasi-experimental control group design, the current study examines two methods of inquiry-based science education which aim to enhance children’s language and science outcomes.

Based on social constructivist theories, children need guidance of more competent partners (e.g. preschool teachers) to develop accurate scientific concepts and language skills (Bronfenbrenner & Morris, 2006; Vygotsky, 2012). This guidance is mostly achieved through discussions, because concepts are constructed through language and language is acquired through conversations (Schleppegrell, 2004).
Related to this is the evidence based concept of sustained shared thinking (Siraj-Blatchford, 2009) which can be found in preschool science education (Hopf, 2012). It is defined “as an effective pedagogic interaction, where two or more individuals ‘work together’ in an intellectual way to solve a problem, clarify a concept, evaluate activities, or extend a narrative” (Siraj-Blatchford, 2009, pp. 78–79). In such interactions language is used for reasoning processes, which foster the construction of knowledge (Mercer, Dawes, & Wegerif, 2004). For this purpose, children have to acquirethe language needed to participate in sustained shared thinking, called academic language (Schleppegrell, 2004).
Structurally, it approximates written text – even in oral conversations – which implies that “it tends to be less personal, more abstract, more lexically dense, and more structured than the face-to-face everyday language” (Gibbons, 2006, p. 4). These features apply particularly to the language of science (Schleppegrell, 2004) and conversations in 'context-reduced' situations (Gibbons, 2006). Context-reduced suggests that speakers discuss an issue which is not physically present in the conversation and that there is an “information gap” between speakers and listeners (Gibbons, 2006). It follows from the above that science education is likely to foster academic language development (Schleppegrell, 2004) and that it is even more likely to achieve this aim if shared reasoning processes occur in context-reduced conversational situations (Gibbons, 2006).
Apart from these pedagogical interactions, a structured learning environment is required to foster the development of scientific concepts in children: Hardy, Möller, and Stern (2006) compared the conceptual development of floating and sinking in primary school students in two learning environments, which both contained experimental learning sites and discussions. In one treatment structure was provided (1) through “sequencing of content”, i.e. each lesson focussed on a specific aspect of floating and sinking, and (2) through teacher contributions to the discussions to enhance sustained shared thinking. The other treatment lacked both types of structure. Children in the structured learning environment made greater progression in their scientific concept development, a difference still observed in a follow-up test one year later.
It can be concluded that structure is needed to develop scientific concepts, but it is not entirely clear which kind of structure (sequencing of content, or structured discussion, or both) might have a greater impact. To answer this question only one kind of structure should be varied.

Based on these findings, the present study examines two methods differing in sequencing of content (aimed at scientific concept development) and context-reduction (aimed at academic language development), (1) with regard to their impact on the development of scientific concepts and academic language in preschool children; (2) if this impact is different according to differences in children’s pre-test-scores in science concepts and language skills; (3) if these differences correlate with differences in sustained shared thinking.

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