Self-regulating strategy development (SRSD) writing instruction is an evidence-based approach that has been shown to increase students’ writing performance and knowledge of writing. The purpose of this study was to investigate whether early elementary students’ story writing performance and knowledge of writing would change following 5 weeks of SRSD writing strategy instruction implemented by their classroom teacher during the second of four terms, in a whole-class setting. Students’ (N = 17) stories at preintervention and postintervention were assessed for essential story components. Students also completed a writing knowledge questionnaire at preintervention and postintervention. Results showed that students’ writing performance and knowledge of writing improved after the intervention. The present study contributes to SRSD writing research by focusing on teacher-implemented whole-class instruction with 6-year-old students in New Zealand.