This study developed and implemented an elementary English writing program using image-generative AI to examine its effects on students’ writing abilities and affective domains. The program was designed following the ADDIE model and aligned with the 2022 Revised English National Curriculum. It used Padlet’s ‘I Can’t Draw,’ allowing students to create images based on their prompts. Eighty sixth-grade students participated, with data collected through pre- and post-writing tests, affective domain surveys, student work, reflections, and teacher interviews. A mixed-methods analysis, combining ANCOVA and content analysis, revealed the following: (1) The program improved the syntactic and lexical complexity and fluency of students’ writing, but not accuracy. (2) Students’ situational interest significantly increased, but individual interest did not. Additionally, students’ engagement and motivation in learning English improved. These findings indicate that image-generative AI is an effective tool for enhancing English writing lessons and providing feedback. The study also emphasizes the critical role of teacher competence in successfully integrating AI into language instruction.