Understanding students' progress towards meeting grade-level expectations within an academic year is the goal of many education stakeholders so that they can make decisions to adjust instruction and improve students' learning trajectories. The purpose of this study was to explore 4th and 5th grade students' progress towards meeting expectations in writing, using a curriculum- based measurement metric. Typed writing samples in narrative, persuasive, and passaged- based informational genres were collected in a one-year longitudinal design with four time points. Multilevel change models revealed evidence of quadratic change across the school year with significant change in the narrative genre but no statistically significant change in the other genres. Type of change (fan-spread growth or mastery learning) and growth based on initial transcription, spelling, and reading abilities were also explored. [This paper was published in "Assessing Writing" v50 Article 100567 2021.]