The main objective of this study was to analyze what writing measures, or combination of measures, would be most appropriate for early detection of students at risk of presenting future difficulties in learning to write in Spanish, in terms of tasks, scoring indices (dependent, independent and accurate-precision) and duration. A sample of 231 first graders was scored through IPAE ("Indicadores de Progreso de Aprendizaje en Escritura" [Indicators of Basic Early Writing Skills]), a curriculum-based assessment, in fall, winter, and spring. The students were classified as at-risk or not at risk based on a standard instrument (EGWA, Early Grade Writing Assessment) administered to them in spring. The predictive usefulness of the IPAE measures and their diagnostic accuracy were analyzed using the ROC Curve and binary logistic regression. The results suggest that dictated arbitrary spelling, dictated rule-based spelling, and dictated nonsense words could be an effective single measure to be used as a universal screening in the first stage of a two-stage gated screening procedure. A combined measure that includes a combination of these tasks and allographs in 1 min and dictated sentences can be efficient in a second stage.