Longitudinal Effects of Flipped Learning on English-Major EFL Students’ Essay Writing Development

Writing remains a persistent challenge for English-major students in Vietnamese university English as a Foreign Language (EFL) programs, where academic essay production requires the integration of content development, communicative purpose, organization, and language control. This study aimed to examine changes in students’ essay-writing development during an eight-week flipped-learning intervention and to identify their relative strengths and weaknesses across key writing components. A longitudinal quasi-experimental design was employed with sixty-two purposively selected English-major students at Hanoi Law University during the second term of the 2025–2026 academic year. Data were collected through three B2 CEFR-aligned essay-writing assessments administered as pretest, posttest 1, and posttest 2. The essays were assessed according to content, communicative achievement, organization, and language. Quantitative data were analyzed using SPSS version 27, including descriptive statistics, paired-sample comparisons, and repeated-measures analysis. The results revealed statistically significant improvement from the pretest to posttest 1 and from the pretest to posttest 2, with the larger gain observed at posttest 2. Repeated-measures analysis showed significant improvement in students’ essay-writing performance across the three assessment points during the flipped-learning intervention. Componential analysis showed that organization was students’ strongest area, whereas language remained the weakest. The study concludes that flipped learning can support sustained EFL essay-writing development when pre-class preparation is coherently connected to feedback-rich classroom practice. Pedagogically, the findings suggest that flipped writing instruction should be complemented by explicit language-focused support, especially during collaborative drafting, revision, and post-feedback refinement stages in Vietnamese universities.