A New Zealand (NZ) version of Word Identification Fluency (NZWIF) was administered to 120 children in their second school year at the beginning, middle, and end of the year, along with a curriculum-based measure of oral passage reading fluency at mid- and end-year. Outcome measures included standardized and high-stakes school-used indicators of literacy achievement. NZWIF generally correlated robustly, concurrently and predictively with criterion measures. Overall, NZWIF performance improved across the year. Performance, and change in performance, varied for students who were and were not judged to be making adequate reading progress. Although at-risk readers performed more poorly at each time point, predictive relations of earlier NZWIF performance, subsequent NZWIF growth, and the interaction of earlier performance and growth to later outcomes varied as a function of proficiency and time of year. Findings extend the evidence-base for curriculum-based word reading measures in beginning reading, and reinforce the need for a developmental approach to assessment research and practice.