This ERS "Focus On" discusses curriculum-based measurement (CBM), the most widely used research-based method for student progress monitoring, which is required in Response to Intervention (RTI) approaches. CBM is supported by nearly 30 years of empirical evidence of its effectiveness in monitoring student progress to increase achievement. Teachers administer short, standardized probes, chart the data, and modify instruction as needed. Sample Data Chart is appended. (Contains 1 figure, 1 table and 7 web resources.)