This study investigated correlates that might explain variance in beginning sight-singing achievement, including tonal discrimination, reading fluency, reading comprehension, and academic ability. Both curriculum-based and standardized tests were used, including the Intermediate Measures of Music Audiation, Otis-Lennon School Ability Test, and Dynamic Indicators of Basic Early Literacy Skills. Sight-singing ability of second-grade students (N = 170) was individually assessed for pitch accuracy only using four-note tonal patterns following a 16-week instructional period and again 8 weeks later following a period of no practice. A factor analysis explained 62% of the variance across 13 variables, revealing correlated factors of Music Ability, Reading Ability, and Academic Ability. Regression analyses with individual variables as predictors indicated that significant variance in sight-singing achievement beyond that explained by pitch matching ability could be explained by reading comprehension ability. Similar results were found with both sight-singing tests. Findings are discussed in relation to Patel's shared syntactic integration resource hypothesis and the need to advocate for music education programs.