After three years of schooling, some primary students are behind expected levels for spelling achievement. This study investigated students’ own explanations of their developing understandings about spelling in the context of classroom writing. Participants were two groups of Year 4 students, one achieving below and one achieving at the expected level in spelling and writing. While the average achievers successfully combined strategies, those below average tended to use one strategy at a time, and seldom made links to prior knowledge. To improve both groups’ spelling, teachers needed to foster metacognitive awareness of strategy use and give specific strategy instruction and feedback to students.