Recent education reform efforts are at the forefront of educators' minds across the nation, science teachers notwithstanding. At least 48 states have developed a mandated standardized test, the majority of which also publish an individual school proficiency report (Olsen, 2001). Washington State's new standardized science test is an example of such reforms efforts. The Washington Assessment of Student Learning in Science (Science WASL), which is administered at the fifth, eighth and tenth grades, specifically measures science content and process skills using questions from earth, physical, and life science courses (Partnership for Learning, 2003). In addition to content knowledge, the Science WASL requires that students think critically, solve problems, apply reasoning skills, and design novel laboratory investigations (OSPI, 2003). The Science WASL is one of several mandated tests that students will have to pass by the year 2010 to earn their Certificate of Academic Achievement in Washington State, (OSPI, 2005). Standardized science tests in other states have similar requirements, drawing both on content knowledge and the critical thinking skills necessary for designing experiments from given scenarios. To best prepare students to take such an assessment, science educators must make careful decisions about teaching both science content and process skills. Many educational researchers contend that students learn skills best and gain better attitudes toward science through authentic, inquiry-based science instruction (Freedman, 1996; Udovic et. al., 2002; Gibson & Chase, 2002; Ad-Marbach & Sokolove, 2000). Inquiry science lessons, according to the National Research Council (1996), are: Multifaceted activities that involve making observations; posing questions; examining books and other sources of information to see what is already known; planning investigations; reviewing what is already known in light of experimental evidence; using tools to gather, analyze, and interpret data; proposing answers, explanations, and predictions; and communicating results. Inquiry requires identification of assumptions, use of critical and logical thinking, and consideration of alternative explanations. (p. 23) Successful implementation of authentic inquiry, however, is no easy task for even the most experienced teachers. Though the National Research Council (1996) mandates teaching science through inquiry, science educators are often reluctant to deviate from more traditional methods (Yerrick et. al., 1997). Lack of funding, poorly selected curriculum materials, insufficient laboratory preparation time, and discomfort with scientific methodology can be difficult issues for science educators to overcome (Chinn & Malhotra, 2001). An advantage of inquiry instruction quickly surfaces when one delves deeper into the available research. Students who received science instruction through inquiry may have an advantage on standardized tests over those who have been taught through more traditional methods (Schneider et. al., 2002). Student achievement on such measures has never been more important. Recent mandates such as the No Child Left Behind Act (2003) will directly affect how federal monies are allocated to schools that fail to meet standards. Ultimately, the reputation of the school and the jobs of administrators and teachers may hang in a precarious balance according to how well students perform on state mandated standardized tests. Given the high-stakes nature of such tests, and the research-based effectiveness of inquiry, it seems imperative that science educators implement more inquiry activities within their classrooms and examine their relationship to student performance. Purpose This classroom-based study focused on whether the inquiry-based activities would enhance students' ability to design laboratory investigations such as those presented on the Science WASL. …