Case studies of Authentic Intellectual Work (AIW) in the Iowa project included four high schools that have been practicing this professional development model for the last five years. The schools, AHST Secondary School, Cedar Falls High School, Spencer High and Middle Schools and Valley High School were visited in April, 2011. The visits included observations of AIW team meetings and interviews with administrators and teachers. Of the four schools, AHST, serving four rural communities, was the smallest school with 150 students seventh through twelfth grade. Valley High School in West Des Moines was the largest with 1,900 tenth through twelfth grade students. Each of the four schools used a phased-in approach to implementing AIW. A core group of teachers was initially trained in AIW, piloted the system, and then additional groups were added until all staff members were included in AIW. Five major themes were identified in the case studies: (1) Administrators and teachers interviewed said they believe that student achievement and learning has improved because of AIW; (2) Teachers and administrators interviewed said that student engagement has improved because of AIW; (3) AIW teams enhance teacher collaboration by using a common language to score and discuss instruction, assessment tasks or assignments, and student work. This has resulted in an improved professional culture within the schools implementing AIW; (4) Teachers involved on AIW teams have improved their practice; and (5) A number of important challenges to AIW implementation should be addressed. The four schools cited multiple examples of how AIW has been advantageous to students, teachers, and administrators. Appended are: (1) Total Number of Students by Subject and Grade in AIW and Non-AIW Schools; (2) Linear Equating Formula; and (3) Achievement Tables for All Grades. (Contains 11 tables, 8 figures, and 2 footnotes.)