Some high schools are moving towards standards-based grading in an attempt to produce consistent grading practices; however, the change's impact on college readiness is not clear. The purpose of this study was to explore the effect of high school's grading practices as it relates to ACT scores and grade point averages (GPAs). Existing data were collected from two comparable high schools using different grading practices in a Midwestern state as determined by state department of education-provided demographics: enrollment, socioeconomic status (as defined by percentage of students receiving free or reduced lunch), and ethnicity. Stepwise multiple linear regressions were used to determine if GPA and the method of high school grading practices, standards-based grading or traditional grading, used predict ACT scores. The findings revealed GPAs remain unchanged and ACT scores may be negatively impacted when high schools utilize standards-based grading practices. In addition, traditional grading practices were a small factor combined with GPA in predicting ACT scores.