In this study of 211 teacher work samples derived from a professional development programme, teachers' conceptualisations of student inquiry were revealed by examining the nature of perceived outcomes and the role of critical thinking that animated teachers' student inquiries collected over nine years. Using a schema adapted from the literature, this paper presents a taxonomy of inquiry outcomes as engagement, as a means to develop content and skills, and as an end in itself. Results show that teachers utilised inquiry predominantly as a means to support student learning of content knowledge and skills. Descriptions of exemplar projects and three representative case study portraits reveal both how teachers perceived inquiry outcomes and the nature of student thinking. Researchers concluded that inquiry outcomes are a result of teachers' choices, particularly in relation to assessment practices. Moreover, inquiry-as-ends more consistently leveraged support for critical thinking than other outcomes. Professional development should attend to teachers' articulation of their purposes for inquiry to better enable teachers to develop inquiry activities that promote students' critical thinking.