Beyond Level Labels: Profiling Vertical Grammar Salience in Taiwan’s CEFR-Referencing K–12 EFL Textbooks

The Common European Framework of Reference for Languages (CEFR) provides widely used proficiency labels, but these labels do not specify how grammar is materially distributed, sustained, or reweighted across school textbooks. This study profiles vertical grammar salience in Taiwan’s CEFR-referencing K–12 English-as-a-foreign-language (EFL) textbook ecology by examining the relationship between English Grammar Profile (EGP) benchmark placement and textbook distributional salience. The corpus consisted of 57 ministry-approved student books from multiple textbook series across primary, junior-secondary, and senior-secondary stages, comprising 234,134 cleaned English tokens. An EGP-derived inventory of A1–B2 grammar points (GPs; N = 602) was consolidated, operationalized as corpus-queryable patterns, and searched in the textbook corpus. Frequencies were normalized as frequencies per million words, transformed as ln(FPM + 1), and standardized as z scores to estimate distributional input intensity. Two complementary clustering analyses were conducted. Level-based clustering identified within-level salience bands for A1, A2, B1, and B2 GPs, whereas stage-based clustering examined how the attested inventory was redistributed within each school stage. Dispersion across books and persistence across stages were used as interpretive complements to frequency-based intensity. The results showed that 12.9% of the benchmarked A1–B2 inventory was unattested in the corpus, that all four CEFR levels contained internal salience stratification, and that senior-secondary materials displayed a compressed distribution in which the largest group of A1–B2 items fell into the lowest salience band. This senior-stage pattern is interpreted cautiously as possible selective recycling of lower-level grammar, while also allowing for the alternative possibility that A1–B2 items recede within more advanced textual input beyond the study’s inventory. The study contributes a transparent, distribution-sensitive framework for diagnostic review of CEFR-referencing textbook systems. Its findings index materials-based availability and distributional prominence, not instructional salience, classroom enactment, or learner acquisition.