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formative assessment probes

Concept-Based Probes: The Justified List

Science and Children—July/August 2021 (Volume 58, Issue 6)

By Page Keeley

The formative assessment probes developed for the Uncovering Student Ideas in Science series fall under two general types: concept-based probes and phenomenon-based probes. Concept-based probes come in several different forms. One of my “signature forms” for developing concept-based probes is the justified list. In this column I describe the use and development of a justified list concept-based probe that is used to check for conceptual understanding.

A concept-based probe reveals how children think about a concept before, during, or after instruction. A scientific concept is a mental construct that gives personal meaning to an object, event, action, characteristic, or process children encounter during science learning. When children understand a concept, they can think with it and use it appropriately. Examples of many concepts children encounter during elementary science include plants, animals, life cycles, decomposition, forces, reflection of light, weathering, weight, evidence, phases of the moon, and weather. Concepts can be formed before children even have a word for the concept. For example, they can mentally construct the concept of the decay of an apple before they are introduced to the word decomposition. In other words, they already have a concept of decomposition before being formally introduced to the terminology. It is important to consider how students think about words we use in science to determine whether they have a concept of that word and how they use that concept in their thinking.

Take the concept of matter as an example. Using the NSTA Next Generation Science Standards (NGSS) Hub’s keyword search for grades K–5, the word matter appears five times in the performance expectations (e.g., 5-LS-2-1: Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment.); 15 times in the disciplinary core ideas (e.g., grade 2 PS1.A: Different kinds of matter exist and many of them can be solid or liquid depending on temperature. Matter can be described and classified by its observable properties.); and four times in crosscutting concepts (e.g., grades 3–5 Energy and Matter: Matter is made of particles.). Clearly matter is a concept that should be checked for understanding before expecting children to think with and use the concept of matter in these three dimensions. A justified list formative assessment probe can reveal how your students think about the concept of matter so that you can make instructional decisions to address flaws or gaps they may have in their understanding of the concept as they engage in learning about matter.

Figure 1 is an example of a justified list for grades K–2 that address the concept of matter (Keeley 2013a). Figure 2 is a similar probe that is designed to be used with grades 3–12 (Keeley 2019). As you can see from these two probes, a justified list probe has a two-part format. The first part asks students to select from a list examples of things that fit a concept. In these two examples the concept is matter. The second part of a justified list probe asks students to justify why the things they selected on the list are examples of the concept as well as why some are not. Students explain the rule or the reasoning they used to select examples of the concept. All justified list probes use this format.

Figure 1
Is It Matter? Probe.
Figure 2
Is It Matter? Probe.

Let’s deconstruct the development of these two probes to understand what they can reveal about children’s concept of matter and how the answer choices mirror commonly held ideas identified in the research on children’s ideas in science. Before I develop a justified list probe, research articles on children’s understanding of a concept are examined to give insight into commonly held ideas that will inform the list of examples and non-examples on a justified list. This research is summarized in the teacher notes that accompany each probe. Several research studies reveal that students of all ages think of matter as something that is tangible—it can be seen, felt, has weight, and takes up space (Bouma, Brandt, and Sutton 1990). Students who think of energy as an ingredient may classify it as matter (Driver et al. 1994). Even students who recite that matter is anything that has weight (or mass) and takes up space fail to recognize gases as matter, and others who think light and heat take up space may classify these as matter. Some students think that everything that exists, including energy, is matter (Lee et al. 1993). One Israeli study of children ages 6–13 found that children had difficulty selecting examples of matter from a list that included biological materials (Stavy 1991). Interviews with students or classroom experience also reveal insights into their concept of matter. For example, some children struggle with things that are very large or very small (microscopic) as being matter. Others easily recognize hard, rigid objects as matter but struggle with soft objects and some liquids. These children’s ideas, both from research and experiences with students are used to develop the answer choices on the justified list probe “Is It Matter?”. For the K–2 version (Figure 1), fewer choices are provided and the examples are everyday familiar objects and materials. There is also a visual image for each item on the list. For the grades 3–12 version (Figure 2), there is a wider range of choices, with some being more abstract. When using a justified list probe that cuts across elementary, middle, and high school grade spans, it is important to remove items that elementary children have little familiarity with or are concepts they encounter in the middle or high school grades, such as cells and atoms.

A justified list probe gives students the opportunity to share their thinking about a concept and provides the teacher with valuable information that informs next steps that will be taken during the instructional cycle to address “missed” conceptions. For example, if students do not select living things on a list, it is a signal to the teacher that even though students may be learning about matter in a physical science unit, it is important that they are given the opportunity to develop the generalization that applies to examples of matter beyond the ones students encounter in physical science. If they struggle with things that are very small and can’t be seen, it is important to develop the idea of small particles of matter.

A justified list probe is versatile in its use. It can be used as a written quick check given prior to instruction and analyzed in order to inform teaching during students’ discussions, investigations, activities, and other opportunities to learn. Justified lists can also be used interactively in small groups as card sorts where each of the items are printed on cards and groups discuss, argue, and sort them as examples, non-examples, and ones they are not sure of or do not all agree on (Keeley 2016). They can also be used with the claim cards strategy and the group Frayer model (Keeley 2015). See the “Is It a Solid? Claim Cards and Argumentation” article in the July 2013 issue of Science and Children and “Is It a Rock? Continuous Formative Assessment” article in the April 2013 issue for more information on using these two formative assessment techniques. After students have had the opportunity to learn and work through examples that did not fit their initial concept of matter, the probe can be used again a second time, checking for students’ conceptual understanding and providing an opportunity to change their initial answer choices and explanations using their new or strengthened understanding of the concept.

Developing justified list probes collaboratively with colleagues is an excellent way to engage in professional learning that can result in an expanded set of classroom formative assessment probes beyond the ones that are available in my books. After reading this article together and examining other examples of justified lists in the Uncovering Student Ideas series, teachers can facilitate and follow the steps listed below in creating their own justified list probes. Of the dozen or more different types of probes in the Uncovering Student Ideas series, the justified list is the easiest one for teachers to develop and a good starting point for developing your own probes.

Steps in Developing a Justified List Probe

  1. Select a concept from your curriculum that students are expected to use. Look for concepts in the disciplinary core ideas or your learning targets.
  2. Create the prompt for part 1 of the probe. The prompt should ask students to select from a list the items that are examples of or match the concept.
  3. Develop the answer choices. Examine any available research on commonly held ideas to identify examples for your list and/or use the wisdom of your experience with students to identify examples and non-examples. For younger students, choose everyday familiar items for the list and include a visual. For older students, select items they have some knowledge about. Choose no more than 12 items for K–2 and up to 25 items for grades 3–12. Decide whether all the items on the list will be examples of the concept or whether there will be a mix of examples and non-examples.
  4. Add justification to part 2 of the probe. Ask students to explain their thinking and/or provide the rule or reasoning they used to select examples.
  5. Make up a title for the probe and add a graphic for the grades 3–12 probes. The graphic can be one of the items listed in the probe.
  6. Create a model answer for the probe. Try out the probe yourself before giving it to your students. What would a best answer look like? If you have trouble with any of the items on your list, then they may not be suitable for your students.
  7. Get feedback. Share your probe with your colleagues for feedback and revise for improvement.

For more information on the different types of probes in the Uncovering Student Ideas series, go to and click one of the books listed. A description of each probe is given for that book. At the end of each description, the type of probe is listed. And finally, as you develop your own probes, please keep this tip in mind from my own experience—a good probe takes two or more revisions before it is in ready-to-use form.


Page Keeley ( is a science education consultant and the author of the Uncovering Student Ideas in Science series (


Bouma, H., I. Brandt, and C. Sutton. 1990. Words as tools in science lessons. Amsterdam: University of Amsterdam.

Driver, R., A. Squires, P. Rushworth, and V. Wood-Robinson. 1994. Making sense of secondary science: Research into children’s ideas. London: Routledge.

Keeley, P. 2013a. Uncovering student ideas in primary science: 25 new formative assessment probes. Arlington, VA: NSTA Press.

Keeley, P. 2013b. Is it a rock? Continuous formative assessment. Science and Children 50 (8): 34–37.

Keeley, P. 2013c. Is it a solid? Claim cards and argumentation. Science and Children 50 (9): 26–28.

Keeley, P. 2015. Science formative assessment: 50 more strategies for linking assessment, instruction, and learning. Thousand Oaks, CA: Corwin Press.

Keeley, P. 2016. Science formative assessment: 75 strategies for linking assessment, instruction, and learning, 2nd edition. Thousand Oaks, CA: Corwin Press.

Keeley, P. 2019. Uncovering student ideas in science: 25 formative assessment probes, 2nd edition. Arlington, VA: NSTA Press.

Lee, O., D. Eichinger, C. Anderson, G. Berkheimer, and T. Blakeslee. 1993. Changing middle school students’ conception of matter and molecules. Journal of Research in Science Teaching 30 (3): 249–270.

Stavy, R. 1991. Children’s ideas about matter. School Science and Mathematics 91 (6): 240–244.

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