This report provides guidance for a rigorous science curriculum in the middle grades based on a solid set of essential standards that can prepare all students to perform at least at the basic level of proficiency and for increasing percentages of students to perform at the proficient and advanced levels. This report is organized around 19 Readiness Indicators: five Process Readiness Indicators and 14 Content Readiness Indicators. These 19 indicators represent the essential knowledge and skills for investigative-based college-preparatory high school science. Content knowledge and process skills are at the core of a solid science curriculum and each is an integral part of the other. The description of each Readiness Indicator includes examples of how the indicator relates to the preparation of students for rigorous high school science and suggestions to help teachers teach the concepts and skills. The 19 Readiness Indicators can guide curriculum planners, principals and teachers in examining what they currently teach, how they teach it, and how deeply they engage students in each of these areas of scientific knowledge and skills necessary for success in rigorous high school science. Teachers can use the Readiness Indicators to identify weaknesses in their assignments, assessments, process skills and gaps in their local curriculum guides.