Movement is essential for learning. Previous research explored the relationship between movement and academic performance, however, evidence regarding the specific gross motor skills related to reading and spelling is lacking. The current study, therefore, investigated the effect a perceptual-motor intervention had on the relationship between gross motor proficiency and letter knowledge in selected Grade 1 (6 to 7-year-old) children (N = 97). Motor proficiency was measured using the Bruininks-Oseretsky Test of Motor Proficiency, Second Edition (BOT-2) and letter knowledge was assessed using the ESSI reading and spelling tests. The study found that a perceptual-motor intervention was effective in significantly improving both fine and gross motor proficiency skills, as well as reading and spelling (p < 0.01). Results also revealed a positive correlation between overall motor proficiency and letter knowledge. Significant relationships were found between reading, spelling and the following gross motor skills (p < 0.01): bilateral coordination, balance and upper-limb coordination. The main finding of the study showed that the strongest correlation was between motor proficiency and spelling (r = 0.46). These results support a growing body of evidence suggesting that a child's gross motor development is essential for academic performance. Therefore, the integration of movement within academic tasks is an effective way of promoting both gross motor and learning abilities in Grade 1 children.