In the early twentieth century in the United States, Roman Catholic schools grew in number and became increasingly regulated by state departments of education. This led to the increased influence of public school reform movements in Catholic schools. Some Catholic educators questioned these movements, while others embraced them. Educational measurement strategies, such as IQ and standardised testing, gained support from women religious orders and congregations, who made up the majority of the Catholic teaching force. For pragmatic reasons, they saw some value in the promises of modern educational science for teaching and learning. This practice, however, put them at odds with some of the beliefs and values of their Church. This study demonstrates how Catholic sister teachers attempted to shape the debate on the introduction and use of reform strategies like IQ and standardised testing. It also examines how Catholic sister teachers made use of Catholic beliefs and values to make arguments in favour of IQ and standardised testing in Catholic schools. Using agreed upon Catholic religious tenets and working within their gendered reality, Catholic sister teachers demonstrated how they tried to convince their colleagues, male and female, to come to an understanding around the use of educational measurement.