This quantitative study tested a relationship between the bell schedule models used in Oregon high schools, and mean graduation rates during the school years 2017-2020. One-hundred fourteen public high schools in Oregon with adjusted cohorts of at least 100 students were examined. Bell schedules were categorized by the day/meet pattern as seven period, A/B block, trimester, or hybrid. Inferential statistical testing was completed using an Analysis of Variance (ANOVA), and an Analysis of Covariance (ANCOVA) to control for school population size and poverty; each with post-hoc testing. Results indicated statistically significant differences between mean graduation rates at high schools when categorized by schedule model; with schools using the seven-period bell schedule having the lowest mean graduation rates when controlling for the effects of adjusted cohort size and poverty. Implications for practitioners as well as recommendations for further research are included. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]