A teacher's belief in what he or she can do is often a predictor for how well students may do in their classroom. Working together in a collaborative setting while looking at student work, determining next steps, and setting goals for student achievement can provide the impetus for teachers to change practices, implement different strategies and find success in the classroom. Collaborative practitioner inquiry focused in a single content such as written expression can bring about positive change for student achievement and teacher efficacy. In this study, a collaborative practitioner inquiry process was used to enhance teacher efficacy and increase student achievement in writing. This process was implemented school wide as an integral part of the school's instructional program. Teachers met once each month in Data Writing Team groups to look at student writing in their own classrooms and across their grade level. Based on the writing samples, teachers created SMART goals, determined levels of proficiency, and identified instructional strategies to implement. Data were collected through the administration of a teacher efficacy survey, focus group and individual interviews, student achievement data from pre- and postwriting samples, and observations and interpretations in a research journal. Findings concluded that collaborative practitioner inquiry contributed measurably to most Lake Shore Elementary School teachers' efficacy as teachers of writing especially by enhancing their convictions that they could teach writing and solve instructional roadblocks individually and collectively. In addition, collaborative practitioner inquiry contributed to substantial improvement in Lake Shore students' writing achievement. Teachers' accountability and purposes for instruction were enhanced through opportunities to work collaboratively together. Finally, collaborative practitioner inquiry contributed to students' writing achievement by adding to teachers' understanding of writing instruction and fostering continuously improved teaching practices. As a result of conducting this study, I learned that teachers who have the time to meet, talk, and think together form a greater focus as a grade level and, in turn, a purpose for what they do in the classroom. When teachers find success in their instruction their efficacy increases and as found during this study student achievement increases. [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.]