This study had three main purposes, to (a) determine students' understanding of basic physics concepts, (b) analyze the science concepts and their connection to real-life context in science curricula and teaching materials, (c) evaluate effect of formative assessment probes on students' understanding of selected key concepts. Subjects were 197, 8th grade students who had studied five basic physics concepts. To evaluate students' understanding, a questionnaire consisting of formative assessment probes was administered with 4 multiple choice and 4 open-ended questions. Findings indicated that students had poor conceptual understanding of the concepts. Science curriculum, analyzed in terms of application to real-world contexts, indicated that textbooks included few practical explanations. In an intervention, one public school received formative assessment probes integrated with extra-curricular hands-on science instruction. Pre-post data showed significant increases in students' understanding of basic physics concepts. Finding that these students significantly out-performed other groups implies: (a) the need to include students' prior learning in instruction and (b) the need for more learning time to apply understanding of concepts to real-world contexts.