Duolingo has become one of the most widely used gamification apps for learning English, mostly for vocabulary and grammar. However, there is limited research on its effectiveness in enhancing writing skills. This study aimed to investigate the effect of Duolingo on junior high school students' learning English as a Foreign Language (EFL) writing skills, focusing on the overall score and five components: content, organization, vocabulary, language use, and mechanics. The study used a quasi-experimental design, specifically the non-equivalent control group, involving 41 eighth-grade students in experimental and control groups. Both groups were assigned writing tests as a pre-test and a post-test. The experimental group received an intervention using Duolingo outside the classroom for eight weeks as a supplementary tool, while the control group only received regular English classes. The statistical analysis using the independent t-test and ANCOVA revealed a significant improvement in writing skills in the experimental group (p < .05). It also showed an improvement in all writing components, especially content and organization. The partial eta squared value indicated a large effect of Duolingo (η²p = .878). These findings suggest that Duolingo has the potential to serve as a supplementary tool for improving writing skills in language learning.

CLIL (Content and Language Integrated Learning) incorporates content acquisition and language instruction, allowing students to develop linguistic competencies while engaging with particular topics. This research aims to investigate the effectiveness of CLIL activities in enhancing students' vocabulary, as well as to explore students’ views of engaging in CLIL activities for their learning process. The participants consisted of 21 primary school students with diverse levels of English ability. The study employed a mixed-methods research approach, combining a quasi-experimental study (one-group pre-test and post-test) with a survey. The results indicated that CLIL activities notably improved students’ vocabulary mastery, with post-test scores (Mean: 60,38) surpassing the average pre-test scores (Mean: 58,28). In response to the students' perceptions of their experiences, among 21 students, 15 (71%) indicated that CLIL activities enhanced their interest in English and science. In this study, CLIL activities were carried out by incorporating singing, engaging in games such as flashcards and QNA, and facilitating group discussions. The CLIL activities offer significant contexts for language application, facilitating the effective acquisition of new vocabulary for students. The students demonstrated enhanced vocabulary test scores as a result of the learning activities. The findings indicate that CLIL-based learning significantly enhances students’ vocabulary, and students express a favourable perception of this approach. Educators should incorporate CLIL activities into their instructional methods to create a vibrant and engaging learning environment. Future investigations could delve into the implementation of CLIL across various educational settings and disciplines to fully harness its potential advantages.