The effectiveness of instruction through content and language integrated learning (CLIL) approach and English science textbook word lists (ESTWL) on science vocabulary knowledge and science content knowledge development of Thai EFL secondary school students

This research project aimed to investigate the impact of integrating English Science Textbook Word Lists (ESTWL) into a Content and Language Integrated Learning (CLIL) approach on the Science Vocabulary Knowledge and Science Content Knowledge of Thai English as a Foreign Language (EFL) students. The study comprised two distinct phases. In the first phase, a corpus-based approach was employed to analyze 46 science textbooks in the English Science Textbook Corpus (ESTC). The result was the creation of ESTWL, categorized into Physical Science, Biological Science, and Earth & Space Science Word Lists, validated by 15 subject matter experts. These lists, consisting of 480 technically appropriate word types, aim to aid lower secondary school students in preparing for science classrooms and serve as a valuable resource for science and language teachers in Content and Language Integrated Learning (CLIL) classes. The developed ESTWL series is accessible at https://sites.google.com/view/estwl. In the second phase, a mixed-methods research design was utilized to assess the effectiveness of ESTWL-CLIL lesson plans on 45 students from three levels (grade 7 to grade 9) of secondary school at a large institution in Bangkok. Quantitative data, gathered through Science Vocabulary Knowledge and Science Content Knowledge tests, showed a statistically significant increase in mean scores for both aspects after the intervention. Qualitative results further indicated that students perceived the instruction through CLIL approach and ESTWL positively. This study recommends the incorporation of this vocabulary pedagogy in CLIL settings for the benefit of science and language educators.