This document reports on the first year of the STACI (Systems Thinking and Curriculum Innovation) project, a two-year project which is examining the cognitive demands and consequences of using the STELLA (Structural Thinking Experimental Learning Laboratory with Animation) software to teach systems thinking, content knowledge, and problem solving. The study is also examining the extent to which this approach helps students to acquire higher-order thinking skills and generalize their new knowledge and skills to other areas. Teachers in physical science, biology, chemistry, and social studies at Brattleboro Union High School (Vermont) designed and tested ways to use STELLA; traditionally taught courses provided control. In addition to time constraints, teachers identified five difficult aspects of their task: (1) determining the appropriate sequence of knowledge that should be followed in teaching systems thinking; (2) identifying the points in the curriculum where systems thinking can best be used; (3) developing models that illustrate systems thinking but are simple enough for students to understand; (4) deciding how and when to introduce STELLA; and (5) assessing the effectiveness of systems thinking for teaching particular concepts. Teachers made progress in curriculum development, and students responded well to the new instructional materials. The teacher questionnaire, a class assignment, an analysis of time spent on curriculum topics, and a reprint of an article on the project are appended. (13 references) (Author/MES)