ImSTEAM (Immersive STEAM Academy) is an innovative Erasmus+ Teacher Academies project designed to transform STEAM education in European secondary schools through immersive technologies (VR/AR/MR). The project addresses a critical "contextualisation gap" identified in PISA assessments, where students struggle to apply abstract STEAM knowledge to real-world problems. Working across five countries (Greece, Italy, Belgium, Croatia, and Slovenia) with varying PISA performance levels, ImSTEAM brings together 17 partners including universities, schools, educational technology experts, and policy facilitators. The consortium will develop a comprehensive framework that aligns STEAM competencies with the PISA 2025 assessment framework and delivers them through immersive, scenario-based learning experiences. Key outputs include: the ImSTEAM Pedagogical Framework mapping contextualised competencies; a modular teacher training program with 19 micro-courses; an Immersive Education Platform with AR/VR learning scenarios; a Cross-border Teacher Mobility and Mentoring Program; and an Open Badge Factory for recognizing acquired competencies. The project employs a three-phase methodology of Alignment (mapping STEAM skills to PISA competencies), Classification (embedding them in real-world contexts), and Operationalisation (creating immersive learning scenarios). A structured Ambassador Program and peer-to-peer knowledge sharing mechanisms will multiply impact, while sustainability is ensured through a self-sustaining Teachers' Academy and Content Sharing Platform..