Das Schulbuch, welches umgangssprachlich mancherorts als „geheimer Lehrplan“ bezeichnet wird, steht im Fokus des Beitrages. Die Autor*innen diskutieren am Beispiel des Themas „Schwimmen und Sinken“, welchen Einfluss die Sprache in naturwissenschaftlichen Schulbüchern auf den Erwerb naturwissenschaftlicher Inhalte durch (mehrsprachige) Schüler hat. (DIPF/Orig.) ; A future-oriented science education refers to everyday experiences, (technical) language and current developments in migration and multilingualism (Kahlert 2022). This requires a participatory bringing together of all areas of knowledge and experience in the classroom (Stoltenberg 2004). The article discusses tasks in science teaching from different perspectives (semantics, multilingualism, etc.), using the topic “swimming and sinking”, which appears to be a suitable frame of reference for several reasons: (1) the topic is based on a wide range of research; (2) it refers to a precise content area with the phenomenon of buoyancy and the considerations on force, density, interaction; (3) it connects to the living environment, and (4) follows the discourse of everyday language vs. educational language. Based on these items, the article tackles the question of what impact language in science textbooks has on (multilingual) students’ acquisition of science content. (DIPF/Orig.)