Early identification of learning difficulties is a critical component of the Response to Intervention (RtI) model. In kindergarten, the screening of foundational reading skills can provide a data-based guideline for identifying students requiring a more intensive response-based intervention before starting elementary school. This study examines the classification accuracy and best predictors of a set of Spanish curriculum-based measures administered during kindergarten. The study's sample included 189 students tested in the fall, winter, and spring. Receiver operating characteristic (ROC) analysis was conducted. The composite score of the curriculum-based measurement (CBM) revealed area under the ROC curve (AUC) values of 0.83, 0.97, and 0.94 in the fall, winter, and spring, respectively. Phonemic awareness and letter-sound knowledge were the only isolated measures that demonstrated excellent AUC values throughout kindergarten. Logistic regression models showed that, when entered simultaneously, all measures were significant predictors of reading risk at some moment of the school year.