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February 7th, 2019

The continuous expansion of scientific knowledge makes it nearly impossible to teach all of the pieces of a given science discipline (in detail) for K-12 students. The role of science education is not to teach the memorization of facts, but to prepare students with core knowledge that they can build upon, on their own, in the future. Preparing our students with a set of core ideas and practices allows them to continue their development as scientific learners, users of scientific knowledge, and possibly, as producers of this knowledge.

Next Generation Science Standards (NGSS) have moved teaching science away from covering many isolated facts, toward helping students build a rich network of connected ideas. This network serves as a conceptual tool for explaining phenomena, solving problems, making decisions, and acquiring new ideas.

NGSS focuses on three-dimensional learning which include the following three dimensions: Disciplinary Core Ideas (DCIs), Science and Engineering Practices (SEPs), and Crosscutting Concepts (CCCs).  The NGSS present standards as knowledge-in-use performance expectations, and each performance expectation integrates the three dimensions.

So what does all of that mean?

Even though NGSS have been around for some time, there can still be confusion around the dimensions. A deep understanding of the three dimensions of NGSS—and how they work together—is essential for developing instruction that both proceeds coherently over time and allows students to build this rich conceptual framework. Let’s walk through an overview to start the journey of gaining a deep understanding of the three dimensions—and their value to the teaching and learning of 21 st century science.

Disciplinary Core Ideas (DCIs)

What are NGSS Disciplinary Core Ideas (DCIs)?

Disciplinary Core Ideas (DCIs) form the basis of what most educators would consider “content knowledge,” also known as scientific facts. DCIs are central to every science field, and guide scientists and learners in observing, thinking, explaining phenomena, solving problems, and asking/finding answers to new questions.

These core ideas are organized into NGSS’ four disciplines of science: Physical Science (PS), Life Sciences (LS), Earth and Space Sciences (ESS), and Engineering, Technology and the Applications of Science (ETS). NGSS advises that in order for an idea to be considered core , it “should meet at least two of the following criteria and ideally all four:

  • Have broad importance across multiple sciences or engineering disciplines or be a key organizing concept of a single discipline;
  • Provide a key tool for understanding or investigating more complex ideas and solving problems;
  • Relate to the interests and life experiences of students or be connected to societal or personal concerns that require scientific or technological knowledge;
  • Be teachable and learnable over multiple grades at increasing levels of depth and sophistication.”

NGSS DCIs vs Previous Standards: An Example

DCIs are structured differently from how the previous standards were structured. Each DCI is a conceptual whole that helps guide students’ thinking. They also link to other DCIs to help students form a deeper understanding that they can use to make sense of the world around them. They move classroom teaching away from having students memorize a number of disconnected facts and concepts, to where students develop a connected understanding of a few powerful concepts that they use to make sense of the world and design solutions to problems. Let’s look at an example comparing an older science standard to NGSS:

  • Older science standard 1.a: Students know cells function similarly in all living organisms.
  • NGSS – MS-LS1-2: Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.

In the NGSS performance expectation, students are called upon to show knowledge in one of the selected core ideas (or scientific facts) designated for Life Science at middle school 6-8 (e.g., knowledge of cell function and parts, such as nucleus, chloroplasts, mitochondria, cell membrane, and cell wall). That is the DCI. The other two dimensions (SEPs and CCCs) are present in the performance expectation, as well.

Science and Engineering Practices

What are NGSS Science and Engineering Practices (SEPs)?

The Science and Engineering Practices (SEPs) describe a) the major science practices that scientists employ as they investigate and build models/theories about the world and b) a key set of engineering practices that engineers use as they design and build systems.

The SEPs are not independent, but rather overlap and work synergistically in classrooms. They can be grouped into 3 categories: Investigating Practices, Sensemaking Practices, and Critiquing Practices.

McNeill, Katsh-Singer & Pelletier, 2015
  • Investigating Practices: These practices focus on students asking questions, planning and conducting investigations, and using mathematical and computational thinking about the natural world–resulting in the production of data.
  • Sensemaking Practices: These practices include the many ways that students can analyze and make sense of data while developing models and constructing explanations about the natural world.  
  • Critiquing Practices: These practices are often left out of K-12 science education. Critiquing practices emphasize students evaluating and arguing about different models and explanations, which ultimately helps them develop stronger understandings about the natural world. This category also includes Obtaining, Evaluating, and Communicating Information.

Fitting the SEPs Together

McNeill, Katsh-Singer & Pelletier, 2015

It can be overwhelming to think about the SEPs—especially for those that are new to NGSS. Essentially, students first use their investigating practices (asking questions, planning/conducting investigations, computational/mathematical thinking), to get their data. Once they have data from the investigating practices, they are able to use their sensemaking practices to develop and use models, analyze and interpret the data, and start to construct explanations. Now, with their explanations and/or models, they can focus on critiquing practic es to engage in argument based on evidence and obtain/evaluate/communicate information.

SEP Example

Let’s return to our original example:

  • Older science standard 1.a: Students know cells function similarly in all living organisms.
  • NGSS – MS-LS1-2: Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.

This performance expectation integrates the Sensemaking Practice of Developing and Using Models. The idea of standards including both content (DCIs) and practices (SEPs) is not necessarily new. However, the third dimension of Crosscutting Concepts can take more getting used to.

Crosscutting Concepts (CCCs)

What are NGSS Crosscutting Concepts (CCCs)?

Crosscutting Concepts (CCCs) provide students with a conceptual framework that helps students make sense of new content. They emphasize the need to consider not only disciplinary content, but also the ideas and practices that cut across the science disciplines. CCCs serve as intellectual tools for connecting important ideas across different domains, and provide students with an organizational framework based on behavior and function.

CCCs generally work together to provide clarity in making sense of a phenomena. We can organize the CCCs into three categories: Causality, Systems, and Patterns.

Moulding et al., 2015
  • Patterns guide organization and classification. They prompt questions about relationships and the factors that influence those relationships. Identifying patterns helps scientists to identify phenomena and predict outcomes.
  • Systems provide students with a way to understand the interactions of a system’s components and the concepts that define the system. Scale & Proportion, Change & Stability, and Matter & Energy fall into this category.
  • Causality is the central CCC: it is the HOW and the WHY.  Causality is the key to making sense of a phenomenon. Cause and Effect and Structure & Function fall under this group.

CCC Example:

When we return to our example, we see that the Crosscutting Concept of Causality (specifically Structure & Function) is used in the performance expectation:

  • Older science standard 1.a: Students know cells function similarly in all living organisms.
  • NGSS – MS-LS1-2: Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.

Why are the CCCs on equal footing with the SEPs and DCIs?

To illustrate the importance of CCCs, let’s use an example from a cognitive psychology research study. It focused on the distinction between how expert and novice chess players organize ideas.

Chess experts and novices were shown pieces randomly arranged on a chess board. They were asked to recreate the arrangement of pieces on the board from memory. Novices tended to remember only individual pieces and their position in space. Experts, however, grouped pieces together based on the strategic moves that the piece could make in the game. The experts could then use this conceptual framework to organize and make sense of any configuration of pieces on the board. In general, novices rely on surface features (isolated facts or formulas) to organize ideas, while experts develop and use a conceptual framework, sorting new knowledge using big ideas or broad categories. Sound familiar?

Using surface features like novices is the old way of learning science. Using a conceptual framework like the experts is the new NGSS way of learning science! CCCs help students think like experts by providing them with a conceptual framework around which they can build their understanding and new ideas.

NGSS Performance Expectations: Putting DCIs, SEPs & CCCs Together

As we said, performance expectations integrate the three dimensions: DCIs, SEPs, and CCCs. Let’s look at our example one last time:

  • Older science standard 1.a: Students know cells function similarly in all living organisms.
  • NGSS – MS-LS1-2: Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.

DCI: LS1.A – Describe the function of a cell as a whole and parts of cells

SEP: Sensemaking Practices – Develop and use a model

CCC: Causality – Contribute to the function

Understanding the three dimensions of NGSS is a critical first step toward preparing students for NGSS performance expectations–but, it’s only the beginning. If you have other specific questions about NGSS, leave a comment or contact us!


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  1. Al Sokaitis on February 7, 2019 at 11:59 am

    Makes me want to start my education all over again. A prescription for becoming a life long learner.

  2. Kelly Caporale on February 10, 2019 at 5:58 am

    If NGSS was the standard when I was in school, I may have like and enjoy science. Very interesting article.

  3. Elementary teacher on February 11, 2019 at 12:05 pm

    Wow, very informative article. Very well written and easy to understand. Makes NGSS a little less intimidating and more educator friendly.

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