I raise the problem that religious effects on the education practices of Australian religious schooling have not been measured, despite many claims and the critical size of the sector. The paper seeks to suggest factors to be considered in shaping methodologies for researching this area. Identifying four ways that religious schooling has been perceived and studied, the paper suggests one of them as a way forward into research: the religious purpose/effect model. Nine distinct purposes are then identified and argued to be in dynamic tension with a further three factors: religion/culture interface ideologies, theology, and unattested non-religious ideologies. Research theory is then briefly explored, along with units of inquiry, problems with the use of secular language to describe religious activity, and the need for more explicit researcher-disclosure. (Contains 5 notes.)