Environment-Based PjBL-STEM for Teacher Professional Development: Developing Reflective Writing Skills among Indonesian Senior High School Teachers

ABSTRACT: This study aimed to develop and initially evaluate an environment-based Project-Based Learning integrated with Science, Technology, Engineering, and Mathematics (PjBL-STEM) module for teacher professional development and to examine its potential to improve the reflective writing skills of Indonesian senior high school teachers. The study employed an educational Research and Development design using the ADDIE framework. The module was developed through needs analysis, design, development, implementation, and evaluation, followed by expert validation, a small-group trial, and field implementation. The field implementation involved 20 teachers who participated in six professional development sessions using a onegroup pretest–posttest design. The findings showed that the module achieved high validity (88.8%) and practicality (87.8%). Teachers’ overall reflective-writing scores increased from a pretest mean of 2.13 to a posttest mean of 2.80, representing a 31.5% improvement. The difference was statistically significant, t(19) = 4.00, p < .001, with a large effect size (Cohen’s d = 0.89). Qualitative findings also indicated a shift from predominantly descriptive writing toward more analytical, critical, and action-oriented reflection. These findings provide preliminary evidence that environment-based PjBL-STEM can serve as a promising framework for strengthening teachers’ reflective writing skills within professional development.

Keywords – environmental learning, PjBL-STEM, reflective writing, teacher professional development, senior high school teachers