Curriculum-based measurement of oral reading fluency (CBM-R) is widely used across the country as a quick measure of reading proficiency that also serves as a good predictor of comprehension and overall reading achievement, but it has several practical and technical inadequacies, including a large standard error of measurement ("SEM"). Reducing the "SEM" of CBM-R scores has positive implications for educators using these measures to screen or monitor student growth. The purpose of this study was to compare the "SEM" of traditional CBM-R words correct per minute (WCPM) fluency scores and the conditional "SEM" (CSEM) of model-based WCPM estimates, particularly for students with or at risk of poor reading outcomes. We found (a) the average CSEM for the model-based WCPM estimates was substantially smaller than the reported SEMs of traditional CBM-R systems, especially for scores at/below the 25th percentile, and (b) a large proportion (84%) of sample scores, and an even larger proportion of scores at/below the 25th percentile (about 99%) had a smaller CSEM than the reported SEMs of traditional CBM-R systems. [For the corresponding grantee submission, see ED608204.]