Little empirical evidence suggested that independent reading abilities of students enrolled in biology predicted their performance on the Biology I Graduation End-of-Course Assessment (ECA). An archival study was conducted at one Indiana urban public high school in Indianapolis, Indiana, by examining existing educational assessment data to test whether a relationship between reading proficiency and student performance on the Biology I ECA existed. The Pearson product-moment correlation coefficient was r = 0.712 (P < 0.01). A strong positive relationship between Biology I ECA and Lexile reading scores accounted for 50.7% of the variance. The results suggested that any measure to increase reading levels would increase standardized biology assessment scores.