Foreign language was recently added to Japan's national primary school curriculum. Phoneme-Grapheme Recognition (PGR) skills are a critical step in both L1 and L2 development. Due to its simplistic approach and the lack of new investment in teacher training, research regarding the impact on PGR skills are important. This study tested the relative differences and growth of primary school students' (grades 3, 4, 5, 6) PGR skills across two semesters. Semester-1 (July) and Semester-3 (March) students (n = 256, female n = 130) completed the same PGR test during regular class time. ANOVA and follow-up pairwise tests assessed achievement differences between grades and across the two-semester gap. Difference testing between grades indicated substantial (R[superscript 2] = 0.32 & 0.19) and statistically significant (p < 0.001) differences at both time points. Pairwise follow-up tests pointed to two steps in statistically different ability (grades 3-4/5-6). Longitudinal tests suggested that the current Japanese national elementary school curriculum supports phoneme-grapheme skill development; However, the twostep ability grouping indicated that the current national curriculum is not sufficiently detailed and/or rigorous to ensure annual student improvement in PGR skills.