To demonstrate effectiveness, writing centers collect quantitative and/or qualitative information about and from the students who use their services. A broader understanding of effectiveness requires us to consider both direct measures of writing quality and why some students do not use the writing center. This mixed-methods research followed one entry cohort for two years and found that regular use of our Writing Center was correlated with higher grades in writing-rich courses, regardless of student background. Findings regarding one-time visitors indicate that adopting more flexible pedagogies is key in encouraging them to return.