This article describes how the Advancing Science and Engineering through Laboratory Learning (ASELL) Schools program was developed. ASELL School's directive is to facilitate the embedding of inquiry-based learning in secondary school classrooms through workshop-based teacher professional development (PD). The approach of ASELL Schools is to balance the lessons learned in education research with teacher voices and curriculum requirements in the design and implementation of teacher professional development. This has resulted in a unique workshop experience, where students and teachers work together on open-inquiry investigations. Afterward, teachers and students are separated for pedagogical sessions, and teachers are given time to discuss and share ideas. The discussion is focussed around the key ASELL Schools pedagogical tool, called the 'Inquiry Slider'. We outline an iterative process based on listening to teacher voices, which was used to develop the workshops. We also demonstrate that the Inquiry Slider is an effective pedagogical tool allowing teachers to focus and expand their efforts to bring more inquiry-based learning into their classrooms.