Can the ability to parse unspaced texts (measured by a Text Segmentation Task, TST) index and predict reading efficiency in Spanish-speaking children? A sample of 1112 children (1st to 6th grade) was assessed. Additionally, two subsamples (51 children of 4th-5th grades and 71 children of 1st grade) were followed up. Our results indicate that the TST: a) reflects the acquisition of reading over primary school grades; b) reflects the teacher's judgment about the child's reading development; c) accurately predicts oral reading efficiency one and four years later year, in the former case even after removing the contributions of the IQ and oral reading speed. These results indicate that TST can be used to both index present -and predict future- reading achievements.