Computational thinking is identified as one of the "essential skills for 21st-Century students." [1] Studies of CT in school programs are being funded by many organizations, including the United States National Science Foundation. In this paper, we describe "lessons learned" over the first two years of a research program (PREDICTS: Principles and Resources for Educators to Infuse Computational Thinking in the Sciences) with the goal of developing knowledge of how to integrate CT into introductory high school biology and chemistry classes for all students. Using curricular modules developed by program staff, two in biology and two in chemistry, teachers piloting the program engaged students in CT with computational evidence from authentic tools in order to develop understanding of science concepts. Each module, representing about a week of instruction, addresses science ideas in the prescribed course of study for high school programs. Project researchers have collected survey data on teachers': (1) beliefs about effective science teaching; (2) beliefs about their effectiveness as a science teacher and their students' ability to learn science, and; (3) content preparedness. In addition, we observed module implementation, collected and analyzed student artifacts, and interviewed teachers at the conclusion of module implementation. Preliminary results indicated some challenges (access to technology, varying levels of experience among students) and cause for optimism (student and teacher engagement in CT and the computational tools used in the modules). Continuing research efforts are described in this paper, along with descriptions of the curricular modules and the use of observations and "CT check-ins" to assess student engagement in, application of, and learning of CT.