In a study to evaluate an approach for improving the critical thinking skills of middle school science students, 60 students were given the assignment of completing three guided laboratory activities and writing a report for each. In writing their reports, students were expected to identify the manipulated variable, identify the responding variable, write a statement of the problem, make a prediction, display the data in a well-organized table, depict the data from the table in a graph, and write a conclusion that showed how the data supported or refuted the prediction. Higher level thinking skills demonstrated by such tasks included analysis, synthesis, and evaluation. The student laboratory reports were evaluated using a comprehensive rubric. It was found that repeated use of the guided laboratory activities produced remarkable improvements in students' higher-level thinking skills.