Although the relationship between reading fluency and high-stakes test achievement is well known, studies were conducted in similar contexts. This correlational study aimed to investigate the relationship between reading error types (insertions, omissions, mispronunciations, and total) and reading fluency (rate, accuracy, and prosody) in narrative and informative text and scores and percentiles in high school placement test (LGS). Seventy-seven eighth graders were selected from three different schools from low--socioeconomic status districts. Simple linear regression and partial and Pearson correlations were performed. The results showed that reading error types and reading fluency are significant predictors of LGS. Informative text predicted more variance than narrative text. Interestingly, as omissions in informative text increase, the achievement in LGS increases.