The relationship between reading skills in earlier grades and achieving "Proficiency" on the National Assessment of Educational Progress (NAEP) grade 8 reading assessment was examined by establishing a statistical link between NAEP and the Early Childhood Longitudinal Study (ECLS) grade 8 reading assessments using data from a common sample that took both assessments. The link allowed a comparison between NAEP grade 8 achievement levels in reading and the finer grain and developmentally descriptive ECLS reading proficiency levels. Reading skills students need to master in earlier grades to later reach NAEP's "Proficient" level at grade 8 were identified. Results showed that, in terms of ECLS reading proficiency levels, to have about a 50% chance of reaching "Proficient" in NAEP's grade 8 reading assessment students need to be at level 5 (reading words in context) or higher by spring term of first grade, at level 7 (extrapolation) or higher by spring term of third grade or at level 8 (evaluation) or higher by spring term of fifth grade.