The SIMUL project aims to support teachers and students engaged in a Multigrade Classroom Implementation (MCI) to strengthen STEM (Science, Technology, Engineering, Mathematics) skills and promote digital literacy and environmental sustainability. The term "Multigrade Classroom Implementation" (MCI) is used in literature to refer to educational settings related to multigrade or combined classes, where students of different ages and grades are engaged in a single physical class, facing varying levels of complexity in learning. Although the STEAM (Science, Technology, Engineering, Arts, Mathematics) approach has shown positive responses in teaching and learning mathematics and scientific subjects, it can be even more valuable in multigrade contexts, replacing traditional frontal lessons. Learning through the STEAM approach is based on interdisciplinary and transdisciplinary methods, recognizing interactions between subjects and the complexity of reality.