Inquiry skills are universally recognised as being integral to a contemporary science education where students need to understand the nature of scientific practices as well as concepts. Although inquiry learning is a common practice among primary educators, the development and assessment of inquiry skills is far less practised. There is a need for assessment strategies that can clarify and support students' development of science inquiry practices. The Science Inquiry Assessments (SIAs) have been created, and now further refined, as a tool to promote the assessment of science inquiry skills, independent from content knowledge, to support the teaching of inquiry practices. This paper highlights the approaches used to design and test the validity of the tasks, and the subsequent challenges that were overcome to create the final product. These relate to teachers' perceptions and practices of inquiry skills, their curriculum priorities, and the appeal of implementing engaging inquiry activities. Our observations and teacher feedback validate the final SIAs as an effective strategy to support primary teachers in shifting to a culture of science inquiry assessment.