This study examined the difference between the number of overall students, African-American students, and students with disabilities on a semester 4 x 4 block schedule who were proficient on the North Carolina Biology End-of-Course Test and the number of the same group of students on a traditional 45-50 minute yearlong schedule who were proficient on the NC Biology End-of-Course Test in the state of North Carolina during the 2009--2010 school year. A causal-comparative design was used and three null hypotheses were tested using chi-square analysis. Archival data was used. The results showed that there was a significant association between the number of the overall students and African-American students who were proficient on the NC Biology EOC Test when taught biology on a 4 x 4 semester block versus a traditional schedule. However, no statistically significant relationship existed between the number of students with disabilities who were educated on 4 x 4 semester block schedule and those students with disabilities who were educated on a six or seven period traditional schedule in biology. Suggestions 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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]