This study examined English language textbooks used by third-year junior high school students in Japan and South Korea, a research focus that has been largely neglected in prior studies within the field of EFL. The rationale for selecting textbooks for third-year junior high school students is grounded in the expectation that, at this stage of education, students should develop a deeper understanding of the subject matter and engage with a prescribed volume of reading material. Notably, all Japanese junior high school students, except for those in some private institutions, are required to take and pass a senior high school entrance examination to secure admission. Given that English is a mandatory subject on this examination, it can be reasonably inferred that the texts are chosen to support the progressive development of English reading comprehension skills. Furthermore, in contrast to Japan, in South Korea, English is offered as an elective subject beginning in the second year of high school. Therefore, it is considered appropriate to utilize textbooks from the third year of junior high school, where English remains a compulsory subject ( Chung & Choi, 2016 ). Six textbooks comprising the three most widely used texts in each country were selected. Each textbook consists of multiple units, each comprising various sections. These sections explicitly delineate the specific skills—reading, writing, speaking, and listening—that constitute the primary focus of each unit. Therefore, this study concentrated on the English texts within the specifically designated reading sections. Table 2 lists the titles and publishers of the selected textbooks.

The texts were entered into an Excel spreadsheet for analyzing the various linguistic elements, including the total number of words, sentences, words per sentence, phonemes, phonemes present and absent in L1, and the regularity of graphemes corresponding to vowel phonemes absent in L1.

Cobb’s (2000) Lextutor software was used to evaluate the lexical difficulty of the textbooks. The software systematically categorized the words based on their frequency distribution, organizing them into four distinct categories: the first thousand (K1) and second thousand (K2) frequency bands, the academic word list (AWL), and an “off list” category (Off) comprising words that did not fall within these established frequency bands. This categorization allowed for a comprehensive analysis of the lexical challenges posed by the selected vocabulary.

In addition to lexical analysis, the software toPhonetics (2013) was used to detect and analyze the phonemes within words.

One-way analysis of variance (ANOVA) was used to examine potential differences in the number of words, sentences, words per sentence, difficulty level, and phonemes between the three English language textbooks from Japan and South Korea, respectively. Additionally, a t-test was conducted to assess differences in the number of words, sentences, words per sentence, and phonemes between the Japanese and South Korean English language textbooks. A chi-square test was conducted to investigate differences in word difficulty, L1-absent phonemes, and phoneme-grapheme correspondence in non-L1 vowel phonemes in the Japanese and South Korean English language textbooks.

Table 3 shows the number of words, sentences, and words per sentence in the Japanese and South Korean English language textbooks. In this section, we first examine whether there are significant differences between the three English language textbooks from Japan and South Korea and then examine whether there are differences in linguistic features between the Japanese and South Korean English language textbooks.

An ANOVA was performed to assess differences between the three English language textbooks used in Japanese junior high schools in terms of linguistic features, including the number of words, number of sentences, and words per sentence. The results indicated no statistically significant differences across the three textbooks, F (2, 6) = 5.1, p = 0.98. As the p-value exceeded the significance threshold, no further post hoc analysis was conducted, indicating that the three textbooks contain similar linguistic features.

Similarly, an ANOVA was performed to examine differences in linguistic features across the three English language textbooks used in South Korean junior high schools. The analysis revealed no statistically significant differences between the textbooks, F (2, 6) = 5.1, p = 0.99, suggesting that the three textbooks had similar linguistic characteristics.

To assess whether the difference in the mean number of words in the reading comprehension sections of the English language textbooks from Japan (M = 302.2, SD = 88.1) and South Korea (M = 398.9, SD = 45.8) was statistically significant, a two-tailed t-test was performed at a 5% significance level. The results indicated a significant difference, t (45) = −8.2, p < 0.01, confirming that the mean number of words per sentence in the South Korean English language textbooks was significantly higher than that in the Japanese English language textbooks.

A two-tailed t-test was used to assess the statistical significance of the difference in the mean number of sentences within the reading comprehension sections of the Japanese (M = 33.9, SD = 11.1) and South Korean (M = 41.3, SD = 38) English language textbooks at the 5% significance level, t (47) = −3.1, p < 0.01, indicating a statistically significant mean difference. These findings suggest that the South Korean English language textbooks featured a significantly higher mean number of sentences than did the Japanese English language textbooks.

The independent samples t-test revealed that there was no statistically significant difference in the mean number of words per sentence between the Japanese (M = 9.1, SD = 1.6) and South Korean (M = 9.8, SD = 1.8) English language textbooks, t (46) = −1.6, p = 0.11.

JT: Japanese English language textbook, KT: South Korean English language textbook.

This section compares the vocabulary levels of the three English language textbooks for third-year junior high school students in Japan and South Korea using the three English language textbooks (see Table 4 ). After initially examining potential significant differences between the three English language textbooks from Japan and South Korea respectively, we analyzed the language-level differences between the Japanese and South Korean English language textbooks.

A one-way ANOVA was conducted to compare the difficulty of the vocabularies in the three English language textbooks used by Japanese third-year junior high school students. The results showed no significant differences in vocabulary levels between the three textbooks, indicating uniformity in these measures, F (2, 9) = 4.26, p = 0.98.

Similarly, an ANOVA was performed to examine the difficulty of the vocabularies in the three English language textbooks used by South Korean third-year junior high school students. No statistically significant differences were found between the textbooks in terms of vocabulary level, F(2, 9) = 0.45, p = 0.99. This suggests that the textbooks have similar textual characteristics.

We conducted a chi-square test of independence and found significant differences between the conditions, χ²(3) = 101.4, N = 6632, p = 0.017. Residual analysis indicated that English language textbooks in Japan preferred words from the Off list (p = 0.002) over English language textbooks in South Korea. Analyzing the vocabulary levels of the six textbooks revealed that the occurrence rates of K1, K2, and AWL words were consistent across both countries. However, the occurrence rate of words not included in these three categories (Off) was slightly higher in Japanese English language textbooks.

K1: The most frequent 1000 words; K2: The second most frequent 1000 words; AWL: Academic words; Off: Words not listed in K1, K2, and AWL; JT: Japanese English language textbook; KT: Korean English language textbook.

Table 5 and Table 6 present the frequency of phoneme occurrence in the reading sections of the Japanese and South Korean English language textbooks, categorized by vowels and consonants. In this section, we first examine whether there are significant differences between the three English language textbooks from Japan and South Korea, and then examine whether there are differences in phonemes between the Japanese and South Korean English language textbooks.

JT: Japanese English language.

KT: South Korean English language textbook.

A one-way ANOVA was performed to assess differences in the phonemes between the three English language textbooks used in Japanese junior high schools. The results indicated no statistically significant differences across the three textbooks, F (2, 78) = 3.1, p = 0.99. As the p-value exceeded the significance threshold, no further post hoc analysis was conducted, indicating that the three textbooks contained similar linguistic features.

Additionally, an ANOVA examining phoneme differences between the three English language textbooks used in South Korean junior high schools found no statistically significant differences between the textbooks, F (2, 78) = 3.1, p = 0.99, suggesting that the three textbooks have similar linguistic characteristics.

An independent samples t-test revealed no statistically significant difference in phoneme occurrence between the Japanese (M = 219.3, SD = 226.4) and South Korean English textbooks (M = 213.8, SD = 217.8), t (100) = −0.1, p = 0.9.

A comparative analysis of the phonemes in the Japanese and South Korean English language textbooks, with particular attention to the phonemes present or absent in Japanese and Korean (see Table 7 ). Only 68.3% of the phonemes found in the Japanese English language textbooks corresponded to those in Japanese, whereas 74.7% of the phonemes in the South Korean English language textbooks were shared with Korean. Notably, approximately 11.1% of the phonemes in the South Korean English language textbooks were associated with vowels present in Korean, in contrast to a mere 4.7% correspondence of phonemes to Japanese vowels in Japanese English language textbooks.

A chi-square test revealed significant differences between the conditions, χ²(1) = 362.1, N = 13,922, p < 0.00. Subsequent residual analysis demonstrated a statistically significant preference for non-L1 phonemes in Japanese English language textbooks compared to their South Korean counterparts (p < 0.00).

The findings indicate that, while the South Korean English language textbooks exhibited a greater lexical richness compared to their Japanese counterparts, the number of instances of phonemes absent from the learners’ L1 was comparatively lower. Conversely, the Japanese English language textbooks displayed a more limited vocabulary compared to their South Korean counterparts, yet featured a higher frequency of phonemes absent from the learners’ L1s.

JT: Japanese English language textbook; KT: Korean English language textbook.

This section provides a comparative analysis of the graphemes corresponding to non-L1 vowel phonemes. Vowel phonemes that do not exist in L1 (six phonemes in Japanese and four phonemes in Korean) were selected from the top ten most frequently occurring vowel phonemes. The frequencies and percentages of the graphemes corresponding to each phoneme were subsequently calculated. Following the methodology proposed by Narita (2009) , graphemes that occurred at a rate of 5% or higher were classified as graphemes possessing regular phoneme-grapheme relationships, whereas those with a percentage below 5% were categorized as irregular graphemes (see Table 8 and Table 9 ).

Many irregular phoneme-grapheme correspondences occur in Japanese English language textbooks, particularly in relation to the phonemes /ə/ and /ə:/, which are not present in Japanese. For example, the phoneme /ə:/ is represented by the grapheme <er> in 54% of instances; <ur>, 24%; <ir>, 11%; and <our>, 2% ( Narita, 2009 ).

In Japanese English language textbooks, words such as “hour” are classified as K1 words—those considered fundamental yet possessing rare phoneme-grapheme relationships—and appear more than ten times. In contrast, South Korean English language textbooks exhibit a relatively frequent occurrence of irregular graphemes, primarily with the phoneme /ɪ/. It is exceedingly rare for the phoneme /ɪ/ to appear in the graphemes <ie> in “movie” or <a> in “garbage,” as seen in South Korean English language textbooks. Nevertheless, with the exception of the phoneme /ɪ/, vocabularies with irregular sound-letter relationships in non-L1 vowel phonemes are seldom employed.

The chi-square test conducted in this study found significant differences between the conditions, χ²(3) = 168.6, N = 10213, p < 0.00. Residual analysis further revealed that Japanese English language textbooks exhibited a statistically significant preference for phonemes with irregular graphemes (p < 0.00) compared to South Korean English language textbooks.

The findings indicate that South Korean English language textbooks use a considerable number of non-native phonemes that adhere to established regular phoneme-grapheme relationships, whereas Japanese English language textbooks use a significant proportion of relatively basic-level vocabularies that possess non-L1 phonemes that deviate from conventional regular phoneme-grapheme relationships.

G: Grapheme; K1: The most frequent 1000 words; K2: The second most frequent 1000 words; AWL: Academic words; Off: Words not listed in K1, K2, and AWL.

G: grapheme; K1: The most frequent 1 - 1000 words; K2: The 1001 - 2000 most frequent words; AWL: Academic word; Off: Words not listed in K1, K2, and AWL.