Handwriting is used throughout the school day and is important to demonstrate knowledge. This research evaluated how handwriting instructional practices and intrinsic and extrinsic factors in actual classroom settings impacted learning handwriting over the course of the school year. Findings indicated that extrinsic factors (educational instructional practices, spatial constraints) and intrinsic factors (task cognitive complexity) influenced handwriting performance, but not always in the same way for writing product and process measures. In addition, stronger relationships were found between writing process measures and handwriting fluency than legibility. Even though handwriting improved over the school year, some instructional practices resulted in a widening performance gap as the school year progressed. The impact of these findings for implementing and differentiating handwriting instruction and guiding future research is discussed. (Contains 8 figures and 3 tables.)