California's Kindergarten Readiness Act of 2010 established transitional kindergarten (TK), the first year of a two-year kindergarten program for students affected by the change in the birthdate cutoff for entry into kindergarten from December 2 to September 1. Instead of enrolling in regular kindergarten, students who turn 5 years old between September 2 and December 2 now receive an "age and developmentally appropriate" experience in transitional kindergarten prior to entering kindergarten the following year (California Department of Education, 2016). The Kindergarten Readiness Act also changed the date by which children must turn 5 years old to enter kindergarten from December 2 to September 1, phasing in the new age requirement by moving the cutoff date back one month per year for three years, beginning in fall 2012 and offering TK to students in the affected data range each year. Now that this three-year rollout of TK is complete, and students from the full birthdate range of September 2 to December 2 are receiving TK, practitioners and policymakers are interested in learning more about the TK experience. How is the TK program structured? Who are the teachers teaching TK? How do teachers approach the instruction of these younger students? This fifth short report in a series highlighting findings from the Study of California's Transitional Kindergarten Program focuses on what we have learned about the structure, teachers, and instruction in TK classrooms in the 2014-15 school year. The findings are based on a survey of 200 TK teachers and 184 classroom observations in 20 school districts conducted in spring 2015. (author abstract)