The motivation for the design of this study was to understand the possibility and impact of the involvement of STEM (Science, Technology, Engineering and Mathematics) professionals on school STEM education. This involved two stages, with the design of a set of authentic STEM inquiry activities firstly and implementation in primary classrooms secondly. Five teachers from a local primary school, who were making their first attempt in implementing STEM learning with students at senior primary levels, participated in this study. The teachers worked collaboratively with an Environmental Scientist with support from the research team to design authentic STEM activities to solve a problem which is currently affecting the school environment. The study used a qualitative approach with teachers' pre- and post-concept maps, self-reflections and interviews to capture changes in teachers' STEM conceptions. The findings showed that "School-STEM Professionals' Collaboration" had a positive impact on teachers' conceptions of STEM education and STEM professionals.