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Middle Grades Science Textbooks: A Benchmarks-Based Evaluation

Science 2000. Decision Development Corporation, 1991 and 1995
Earth Science Life Science Physical Science

About this Evaluation Report
Content Analysis
Instructional Analysis

[Explanation] This section examines whether the curriculum material's content aligns with the specific key ideas that have been selected for use in the analysis.
[Explanation] This section examines whether the curriculum material develops an evidence-based argument in support of the key ideas, including whether the case presented is valid, comprehensible, and convincing.
[Explanation] This section examines whether the curriculum material makes connections (1) among the key ideas, (2) between the key ideas and their prerequisites, and (3) between the key ideas and other, related ideas.
[Explanation] This section notes whether the curriculum material presents any information that is more advanced than the set of key ideas, looking particularly at whether the “beyond literacy” information interrupts the presentation of the grade-appropriate information.
[Explanation] This section notes whether the curriculum material presents any information that contains errors, misleading statements, or statements that may reinforce commonly held student misconceptions.


Idea a: The surface of the Earth is changing continually.
There is a content match. This idea is mentioned a few times in a video for grade six in the context of moving continents. It explains that the continents have been moving since the early history of the Earth and that they will continue to move in the future, but makes no mention of changes to surface features of the Earth ( Also, a key concept states this idea explicitly—“The Earth is dynamic” (, LP1, p. 5)—but the idea is not presented explicitly to students. In this lesson, students are asked, “Why don't mountains last forever?” (, LP1, p. 5). While this question implies that mountains change, it does not generalize to the other surface features of the Earth.

Idea b: Several processes contribute to changing the Earth’s surface.

There is a content match. This idea is addressed at all of the grade levels. In grade five, students make models to observe the process of sedimentation and the erosion of mountain ranges (, and In grade six, students examine how environments have changed, including how different processes change the land (students are directed to use the How Land Changes Database []). In grade seven, students study how the land has changed through geologic time (–5), how volcanoes erupt (, and how mountains form ( In grade eight, students reexamine plate tectonics (8.4.23), earthquakes (8.4.24), and volcanoes (8.4.25). In these lessons, students view videos (such as the formation of Surtsey [7.4.33, Video Index]) and still photographs (such as the photos found in the How Land Changes Database), as well as make models of Earth-shaping processes and discuss them.

Idea c: The processes that shape the Earth today are similar to the processes that shaped the Earth in the past.

There is a content match. This idea is addressed in a sixth-grade lesson only ( Students are asked to discuss current geologic changes (erosion, earthquakes, etc.) and if these processes occurred in the past too. The teacher is to explain the principle of uniformitarianism. Lastly, students look at photographs of current landforms and are asked to determine what processes occurred in the past to create them.

Idea d: Some of the processes are abrupt, such as earthquakes and volcanic eruptions, while some are slow, such as the movement of continents and erosion.

There is a content match. In grade six, the objectives for cluster 3 include that students “understand that some environmental change is abrupt while some is slow” (6.1.3, LP, p. 1). The sixth-grade story line for cluster 3 explains that “[w]eathering and tectonic movement are but two of the ways in which environments can be changed, either quickly and drastically, or slowly” (6.1.3, LP, p. 1). Students examine the How Land Changes Database and answer some follow-up questions ( One of the questions asks: “Which of these processes might cause a rapid change in the environment? Which might cause a slow change?” (, SI3–1, p. 1). In the next lesson, the teacher's lesson plan suggests that students categorize and sort these processes in terms of “Changes I Could Notice in My Life” and “Changes I Could Not Notice in My Life” (, LP2, p. 9). In grade eight, students view several different volcanic eruptions and damage from earthquakes. These are relatively fast changes to the surface of the Earth, but their time frame is not mentioned in the videos and still photographs.

Idea e: Slow but continuous processes can, over very long times, cause significant changes on the Earth’s surface.

There is a content match. There are very few places where slow and continuous changes are mentioned, but only one is explained in terms of the small changes that can accumulate to make large changes on the surface of the Earth over long periods of time. In grade six, students watch a video about the movement of the Earth' s continents over time ( This video states that the movement of the continents is far too slow for people to notice it. However, this video mentions only the changing location of continents, and fails to mention other continuous changes to the surface of the Earth, such as mountain formation or river erosion. In other instances, students discuss changes over time, but not specifically that small changes can accumulate over long time periods to create significant changes to the surface of the Earth. For example, in grade seven, students make a model of mountains to explore mountain-building processes. They are asked: “What would happen to your mountain range (supposing it were real) after a million years or so?” (, SI33–2b, p. 883). But there is nothing in this question that would help students to see that the very slow, gradual changes to mountains can create dramatic changes eventually.

Idea f: Matching coastlines and similarities in rocks and fossils suggest that today’s continents are separated parts of what was a single vast continent long ago.

There is a partial content match. The following presentation of Idea f shows which parts of the idea are treated (in bold) and what alternative vocabulary, if any, is used (in brackets): Matching coastlines and similarities in rocks and fossils suggest that today's continents are separated parts of what was a single vast continent long ago. The material presents the evidence (similarities in rocks, fossils and coastlines) and the conclusion (the continents were once joined together) in separate places, but does not relate them. The conclusion, but not the evidence, is stated in grade seven: “In the 1920’s, scientist Alfred Wegener showed how the modern-day continents probably fit together to form a single continent. Wegener called this supercontinent Pangaea” (, S132–4a, p. 860). Later, in grade eight, the material presents evidence but not the conclusion. The lesson plan directs the teacher to pose the following question:
Paleontologists have found the fossils of identical creatures in both Europe and North America. Also, they have found mountain ranges of the same age and rock formations on the two continents. How could fossils and mountain range structures with the exact same age be found on continents separated by 2,000 miles of ocean? Discuss the students' responses. [,LP1, p. 8]

Although this statement does include some of the historic evidence for continental drift, it does not explain that the evidence consists of the clues that scientists used to develop the idea that continents moved. Also, two notes in the teacher's lesson plan may help to present the historic context but seem to be optional, and there are no instructions to help teachers to introduce this information to students. One note in the lesson plan says to have students make continental cutouts and move them to simulate tectonic movement. The other note explains that early map-makers “were impressed by how the east coast of South America seemed to ‘fit’ with the central and southwestern coast of Africa” (, LP1, p. 8). Lastly, two videos show how the coastlines have matched up to form Pangaea (, and 7.4.32), but this phenomenon is not labeled specifically as evidence for the ancient supercontinent.

Idea g: The solid crust of the Earth consists of separate plates that move very slowly, pressing against and sliding past one another in some places, pulling apart in other places.

There is a content match. This idea is mentioned in all grade levels (grades five through eight). In grade five, information about the Earth's moving plates is found in the teacher's lesson plan only. The objectives of lesson 4 include “to discover that Earth's crust is in constant motion” (, LP4, p. 20). Later, the teacher's background section explains, “[T]he crust is divided into pieces, or crustal plates, that move from one place to another over the Earth's surface.... The movement of these plates is the source of all geological activity, including earthquakes and the formation of mountains” (, LP4, p. 20). However, there is no indication that this information is to be shared with the students. During the lesson, the term “plate” used in the explanation of how mountains form, but the term itself is not defined or explained. The first time that students hear about plates is in a class discussion, in which the teacher explains that “[b]eneath the crust lies the mantle, a thick layer of hot, semi-liquid rock, called magma, on which plates of the crust are floating” (, LP4, p. 23). Plates have not been defined, and students have no information about the crust, mantle, and core of the Earth at this point in the lesson.

This key idea is mentioned again in grade six. The cluster 3 story line explains that tectonic movement is one way in which environments can be changed. In one of the activities in lesson 1 of cluster 3, students see photographs and read text from the How Land Changes Database. The description of tectonic movement explains:

[Y]ou can see from this present-day sketch of the continents that each continent is attached to plates below the surface of the land and water [only the continents are included in the sketch; the details of the plates are not shown]. These plates are constantly in motion, but they move so slowly that the changes of their positions can only be seen over long periods of time [tectonic movement is found in the How Land Changes Database]. []

In grade seven, students study how the continents have moved over time. A video is provided that shows the shapes and locations of the continents and how they have changed since Pangaea. The video also shows the outline of the plate boundaries and the three types of plate motion. However, the distinction between plates and continents is not clear. Students also brainstorm what causes the continents to move over time. Students practice this idea only by answering questions that imply that the continents (not the plates) have moved, such as: “What modern-day continents were once part of Laurasia?” (, SI32–4a, p. 860). In grade eight, students return to plate tectonics. They are shown a demonstration of a convection current and watch a video that uses crusted lava to represent how the Earth' s plates interact.

Idea h: Landforms and major geologic events, such as earthquakes, volcanic eruptions, and mountain building, result from these plate motions.

There is a content match. The link between plate motion and the creation of land features and geologic events is made in the sixth- and eighth-grade materials. In grade six, one of the activities has students view photographs and read text from the How Land Changes Database ( The description of tectonic movement explains that “the processes of tectonic movement can take many forms. Earthquakes, volcanoes, and the uplift of mountains are the results of tectonic movement.” In grade eight, students compare maps of earthquakes and plate boundaries ( and of earthquakes, volcanoes, and plate tectonics (

Building a Case

Science 2000 asserts the key Earth science ideas, but does not develop an evidence-based argument to support them.


Science 2000 organizes each unit around an interesting problem or question, such as a suitable storage location for radioactive waste. However, the focus, theme, or topic for the units is never a key Earth science idea itself. These materials frequently make use of key Earth science ideas but rarely develop them. Experiences related to the key Earth science ideas appear in several units in different grades. Given the material's organization, it is important that tasks, questions, or text be provided that clearly tie together the fairly brief and distributed experiences students have had with the key Earth science ideas.

Unfortunately, the material does not include such experiences. While the unit problem does a very good job of framing the activities in a unit, there does not appear to be a plan for the conceptual development of ideas across units. The key Earth science ideas are rarely related to one another. Furthermore, quite sophisticated ideas show up in earlier grades and are repeated in later grades. For example, the idea that the Earth' s surface consists of separate moving plates (Idea g) is introduced first in fifth-grade materials in the context of an activity in which students make a model of mountains ( This key idea is addressed next in sixth-grade materials in the context of changing environments, but with no reminder to students (or the teacher) that they may have encountered this key idea before ( In grade seven, this key idea is addressed in the context of exploring how the continents have changed location over time ( The material does not link these experiences with the experiences students had with the idea in sixth-grade materials.

Not only does the material not tie together the different experiences students have had with a key idea, it does not even alert teachers to the individual instances in which the same idea is treated so that they can design their own ways of tying the experiences together. The unit overviews identify only topic headings (which are usually not specific enough to give any indication about what ideas are addressed), and rarely make mention of treatment of any of the ideas in other units (at the same or earlier grades).

Few, if any, relevant connections are made to concepts outside this set of key Earth science ideas. Although Science 2000 recommends the use of models to show the Earth' s processes, it misses the opportunity to connect its use of models to the role of models in science.

Beyond Literacy

While the text does a nice job of restricting its treatment of this topic to key ideas that are part of science literacy, its presentation of the key Earth science ideas about plate tectonics near the beginning of the fifth-grade unit seems too early for most students to understand. While National Science Education Standards (National Research Council, 1996, pp. 159–160) includes these key ideas in content standards for grades five through eight, Benchmarks for Science Literacy (American Association for the Advancement of Science, 1993, p. 74) postpones the theory of plate tectonics and its explanation in terms of heat convection, gravity, and density until grades nine through twelve.


The evaluation teams developed a summary assessment of the most common kinds of errors found in each of the three subject areas—physical science, Earth science, and life science. In this context, “errors” is taken to mean not only outright inaccuracies, but also those instances in which the material is very likely to lead to or support student misconceptions. Overall, inducement to misconstrue is the most serious problem of accuracy in the evaluated materials.

The evaluation teams’ collective findings, presented below, should be taken as having general applicability to all of the evaluated materials, not complete and specific applicability in toto to any one of them.

Identified errors occur most frequently in drawings and other diagrams. They take the form of representations that are likely to either give rise to or reinforce misconceptions commonly held by students. Following are Earth science examples of the kinds of misleading illustrative materials of most concern to the evaluation teams:

  • Maps that do not show the accurate locations of earthquakes and volcanoes will prevent students from understanding the relationship between these events and plate boundaries. Likewise, diagrams and maps that do not include legends, and photographs that do not explain the size and scale of the object seen, are difficult for students to understand.
  • Diagrams that (a) depict plates moving away from one another, thus exposing the mantle, (b) show the mantle very close to the surface of the Earth, or (c) show plates as being a layer under the crust inaccurately represent the structure of the Earth and the motion of plates.
  • Diagrams that show the melting of subducted plates are incorrect. Subducting plates are known to cause melting in the mantle, and thus nearby volcanic activity, but the plates do not melt.