move teaching away from covering many isolated facts to a focus on a smaller number of disciplinary core ideas (DCIs) and crosscutting concepts that can be used to explain phenomena and solve problems by engaging in science and engineering practices. The NGSS present standards as knowledge-inuse by expressing them as performance expectations (PEs) that integrate all three dimensions from the Framework for K-12 Science Education. This integration of core ideas, practices, and crosscutting concepts is referred to as three-dimensional learning (NRC in Division of Behavioral and Social Sciences and Education. The National Academies Press, Washington, 2014). PEs state what students can be assessed on at the end of grade level for K-5 and at the end of grade band for 6-8 and 9-12. PEs do not specify how instruction should be developed nor do they serve as objectives for individual lessons. To support students in developing proficiency in the PEs, the elements of the DCIs will need to be blended with various practices and crosscutting concepts. In this paper, we examine how to design instruction to support students in meeting a cluster or ''bundle'' of PEs and how to blend the three dimensions to develop lesson level PEs that can be used for guiding instruction. We

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The research reported in this case study explores the understanding of stoichiometry and related concepts of Thai science students in grades 10 and 11 after major national curriculum reforms. Students_ conceptions and alternative conceptions were investigated using a questionnaire -the Stoichiometry Concept Questionnaire (SCQ) (N = 97), which consists of 16 multiple-choice items, the choices for which respondents are required to provide reasons. The findings suggest that less than half of the students surveyed hold what is considered by a panel of experts to be a scientifically acceptable understanding for the conceptions investigated. The main student alternative conceptions are that one mole of all substances has a volume of 22.4 L at STP, that a solution that contains a greater mass of solute has the higher molar concentration, and that the limiting reagent is the reagent for which the lowest mass of reactant is present. Examination of students_ reasons suggests that they resort to the use of algorithms with little understanding of the underlying concepts. It thus seems the national educational reforms have not resulted in a sound understanding of some science concepts. It is recommended that curriculum developers should specify a need for conceptual understanding along with capability in numerical problem-solving in their learning objectives, and link this to assessment regimes that reward conceptual understanding. A need for on-going professional development seems essential if the intentions of the Thai curriculum reforms are to be realized.

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