Organisational signals and sources can be considered metatextual cues that guide the processing of the discourse. Organisational signals encourage readers to use the structure strategy, while source information reveals the epistemic and formal properties of texts. This study addressed three gaps in prior research about these topics: (1) whether organisational signals were useful for 12–14/14–16-year-old students reading causal and sequential texts, (2) the role of sources in single-text understanding, and (3) the relationship between sensitivity to organisational signals (rhetorical competence) and attention to sources. Participants read causal and sequential texts with or without these metatextual cues and wrote a summary. Summary quality was considered an indicator of understanding and using the structure strategy. The number of sources translated into the summaries was considered an indicator of source attention. The results indicated that (1) organisational signals had an effect on summary quality in both age groups and texts; (2) sources did not affect summary quality, but when participants read signalled texts, the number of sources mentioned made a unique contribution to summary quality beyond decoding, general reading comprehension and rhetorical competence; and (3) the number of sources mentioned correlated with rhetorical competence among participants who read the signalled texts. These results suggest that 12–16-year-old students need the aid of organisational signals to launch the structure strategy with causal and sequential texts and that sources may be more useful in combination with organisational signals, but only for students with some level of rhetorical competence, illustrating the intricacy of literacy development.