This mixed-method dissertation study contributes to the literature on teacher teams and collegial supports by employing the use of the team-based construct of backup behavior to measure grade-level team member supports. The results showed that the majority of teachers are actively seeking opportunities to assist grade-level team members, but preventative factors such as not having enough time, having to neglect their own work to assist others, and operating within an environment of team member comparisons impede on these supports. Additional findings identified differences in backup behavior across race/ethnicity, school grade level, team stability, and the grade-level team leader. Given the documented benefits of teacher collegial supports on professional practice and teacher well-being, insights gained from this study can be used to strengthen grade-level teams through the intentional utilization of team member backup behavior supports. Furthermore, I argue that teacher team member backup behavior support can be used as a vital mechanism to lowering teacher attrition rates and maximizing school improvement efforts. [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.]