VietTESOL International Convention 2026

Google AI Studio allows teachers to build language-learning apps customized to the national English curriculum and students’ proficiency levels; however, little research on the effectiveness of these applications has been done. This study examines how SimplEnglish, a teacher-developed, curriculum-aligned, AI-powered application, improves 10th-grade students’ language knowledge and skills. The study employed a mixed-methods research design combining a quasi-experimental approach with a Likert-scale questionnaire and semi-structured interviews. Ninety 10th-grade students, including an experimental group (Class 10A3, n = 46) and a control group (Class 10A4, n = 44), both with comparable English proficiency levels, participated in the 12-week intervention. Data were collected through pre- and post-tests to assess changes in participants’ language knowledge and skills, as well as through the questionnaire and interviews to explore the experimental group’s learning experiences with SimplEnglish. The post-test results indicated that the experimental group showed greater improvement than the control group in vocabulary acquisition, grammatical accuracy, reading comprehension, and speaking fluency but little progress in listening comprehension and writing skills. Besides, data from questionnaire responses and interviews revealed that students had positive learning experiences with SimplEnglish and supported the subsequent integration of the Grade 11 curriculum into the app. These findings suggest the need for further improvement and development of SimplEnglish and emphasize the practical potential of teacher-developed, curriculum-aligned, AI-powered applications in ESL-oriented teaching and learning.