This article explains a mixed methods study utilizing multiple cases in which answers to the question of how cognitive learning theory can influence instruction that maintains the central role that teachers have in the classroom, responding to students' learning needs as they work on authentic tasks. The researcher investigated the responses of teachers to training around a model of instruction incorporating cognitive learning theory. What emerged from the inquiry was a model of instruction based on cognitive apprenticeship titled Cognitive Apprenticeship Learning Approach (CALA). This paper outlines the analysis of CALA based on the fidelity of teachers implementing carefully constructed instruction to apprentice students in writing based on teacher observations and data on student writing after attending targeted professional development. The data were collected from a group of 132 classroom teachers spanning the grades of transitional kindergarten through eighth grade. One consistent finding is that instruction based on a lesson design that focuses on cognitive apprenticeship increases students' ability to write in the early grades. The cross-case analysis revealed that teachers wanted to collaborate with peers or a coach so that it would be easier to write the lessons, and they would know which lessons were stronger than others. The analysis also revealed that teachers felt the CALA training increased their ability to teach writing and that their students' writing had improved overall.