This study explores to what extent principals perceive "instructional program coherence" (IPC) and vertical collaboration occur in high schools and their mid-level feeder schools. It also measures IPC and its five components' association with different measures of student achievement. The study took place in the state of Missouri, and 312 principals of high schools with separate feeder middle schools were invited to participate. Electronic and paper surveys, as well as public data, were collected and analyzed using descriptive statistics, bivariate correlations, and linear regression. The findings show that principals perceive their school's IPC to be fairly strong, but their vertical collaboration needs improvement. The findings also indicate that only particular IPC components such as curriculum, instruction positively influenced graduation rates, academic climate positively influenced the EOC Algebra 1 scores, and vertical collaboration positively associated with higher average freshman GPA's. A major limitation to this study was the low response rate. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]