A sociocultural perspective considers science textbooks as 'cultural supportive tools' with significant cultural missions. By juxtaposing symbolic, mathematical, and visual-graphical text, textbooks present the intertexts deployed by the scientific community to convey conceptual understandings in a way that no one form can. Intertextuality entails two aspects: bridging everyday knowledge with science knowledge, and intertextual links among the different modalities and representations. The aim of this research is to develop and utilise an analytic framework for analysing how intertextual relationships in science textbooks support diverse students' learning. The framework was utilised to discern levels of intertextuality, types of content, and quality of scaffolds in a selection from grade 8 life and physical science textbooks. Intertextuality as the ensemble of different forms of text that 'complement' each other for conceptual learning was evident. However, these forms and representations were not explicitly connected to develop students' competence in navigating the various modalities. Moreover, the science text displayed limited opportunities for eliciting events in students' lives and for leveraging students' knowledge to develop scientific explanations and disciplinary language. Findings are discussed in relation to the textbooks' affordances for providing 'hybrid spaces' for students to coordinate and synthesise multiple representations and modalities for deep understandings.