The purpose of this quantitative study was to explore the impact that teacher teams, specifically building-level leadership teams and professional learning communities, can have on a school's safe and collaborative culture and effective teaching practices. Waves of school reform have made their way through legislation and schools and, as a result, have increased demands placed upon building principals as leaders of their schools. This study utilized a survey adapted from Marzano's High Reliability Schools[superscript TM] framework which was administered to all current Indiana secondary public-school teachers. Inferential analysis indicated that both building-level leadership teams and professional learning communities have a significant effect on a school's safe and collaborative culture and effective teaching. While a principal's participation in the Indiana Principal Leadership Institute (IPLI) was not found to have a significant effect, correlational analysis did determine that a safe and collaborative culture and effective teaching have the potential to effect each other due to a positive linear relationship being found between the two variables. Analysis of research questions resulted in important implications that focus on a principal's development of collaborative teams within their school structure, specifically building-level leadership teams and professional learning communities. The findings and implications of this study, combined with additional supportive research cited within this study, signal to the importance of a principal's responsibility to both develop and support collaborative teacher teams in the buildings they lead. [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.]