Lexia® Core5® Reading performance measures were shown to be valid indicators of reading ability based on comparisons with Rasch unit (RIT) scaled scores from the Northwest Evaluation Association Measures of Academic Progress (MAP). Strong correlations between Core5 performance measures and MAP RIT scores were significant at the beginning, middle, and end of the school year. Additionally, when students are On Target or reach benchmark, their performance in Core5 is associated with proficiency on MAP at the end of the year. These findings indicate that Core5 can serve – not only as an instructional program – but as a key component in a school's literacy assessment.