Thematic Structure and Thematic Progression in Reading Texts in Vietnamese High School English Textbooks

Thematic choices and thematic development are crucial for constructing a meaningful and coherent text, facilitating readers' comprehension. Although extensive studies on textbook analysis have explored either thematic structure or thematic progression patterns, these two aspects seem to have been collectively under-investigated. This study attempts to investigate the differences in thematic organizations that characterize 20 reading texts in English 10 and English 12 textbooks for high school students in Vietnam, to investigate how thematic features in different textbook levels aligns with learners' proficiency levels. Two analytical models, including Halliday's (1994) theme categorization and McCabe's (1999) thematic progression patterns, were adopted. The findings reveal a predominant use of simple, mainly unmarked topical themes in both books, with an increased presence of multiple and clausal themes in English 12. The results also indicate a dominant use of constant, simple linear, and miscellaneous progression patterns, while more complex structures such as derived hyper-themes and split rhemes are rare, and split themes are entirely absent. Hence, these research results suggest a strategic approach to textbook design aimed at enhancing linguistic proficiency and reading comprehension through increased thematic complexity across different language levels, which can offer valuable pedagogical implications and inform future research.