Each of the three categories is described below.
Conceptual Understanding
Mastery of basic scientific concepts can best be shown by a student’s ability to use information to conduct a scientific investigation or engage in practical reasoning. Optimally, essential scientific concepts involve a variety of information, including:
- facts and events learned from science instruction and through experiences with the natural environment;
- scientific concepts, principles, laws, and theories that scientists use to explain and predict observations of the natural world;
- information about procedures for conducting scientific inquiries;
- information about procedures for the application of scientific knowledge in the engagement of practical tasks;
- propositions about the nature, history, and philosophy of science;
- kinds of interactions between and among science, technology, and society.
The goal of school science is to engender conceptual understanding. Students should acquire information in ways that will enable them to apply it efficiently in the design and execution of scientific investigations and in practical reasoning.
A challenge in the design of assessment exercises is to capture changes in the characteristics of student performance as children mature. In the primary years, when the goal of school science is to build a rich collection of information derived from examined experiences with the natural environment, the assessment of conceptual understanding will focus on the breadth of information acquired about the natural world and the student’s ability to elaborate on principles by using personal experiences. Does the student know the cyclical changes in the apparent shape of the Moon over time? More importantly, can the student relate how he or she knows about the changes? What evidence does the assessment exercise provide that the student’s information is based on direct experience? Is there a science notebook in which the student recorded observations of the Moon over time? Does the student know that sometimes the Moon is visible during daylight hours? In the primary years, the focus should not be on explanation or prediction, but instead on knowledge obtained from rich experiences in school. Consequently, assessment exercises would not be concerned with having students explain why the Moon appears to change shape but rather with relationships between time of day, apparent positions of the Sun and the Moon, and times of moonrise and sunset.
In the middle and high school years, the emphasis should shift from richness of experience to reasonable scientific interpretation of observations. In the elementary years, the primary concern should be with how well reasoned the interpretation is presented by the student, not with whether it reflects the most sophisticated scientific reasoning. However, at grades 8 and 12, the assessment should be increasingly concerned with the congruence of the students’ interpretations with accepted interpretations, as well as with the sophistication of their reasoning in moving from observations of the natural world to explanations and predictions. Of special interest in the 2005 NAEP Science Assessment will be the extent to which students are able to understand and use the notions of models, systems, and patterns of change.
It is important to note that many aspects of conceptual understanding as defined for the new NAEP Science Assessment cannot be tested using exclusively multiple-choice items. Items of this kind may be satisfactory for assessing individual parts of the information base, but they are limited in tapping highly valued aspects of conceptual understanding.
Scientific Investigation
Scientific investigation represents the activities of science that distinguish it from other ways of knowing about the world. It incorporates such previously used assessment categories as "processes of science" and "scientific problemsolving." This category is not just another name for the scientific method. Indeed, there is great confusion about the scientific method in the teaching of science. Real science is doing what one can in any way one can, often creatively and insightfully and using flashes of insight with little regard for a progression of steps. However, there is a familiar format and context for reporting the results of experiments. It begins with the report of the problem and continues with the hypothesis, the experimental design, the data collected, the analysis of those data, and the conclusions (if any). This convention of science is often mistaken for how scientists actually work. The results must satisfy logical analysis, but logical ordering may appear only when the report is prepared. A great disservice has been done to generations of students because well-meaning people have taught the standard method of reporting science as the standard method of doing science.
Scientific investigations must be designed at levels appropriate to the development of the students. This component has important implications for assessment. Young students are limited in their ability to perceive the scale of both very large and very small things. Students’ limitations handicap them when they are forced, either by the textbook or by the curriculum, to deal with developmentally inappropriate concepts such as atoms or even cells. Young students are also developmentally limited in their ability to understand time. The distant past and the future are narrowly perceived by the egocentric student. Instruction, as well as assessment, must recognize where the student is and take developmental levels into account. As students develop and accumulate experiences, their performance in doing scientific investigations should begin to look more and more like "real" science.
Central to the ways scientists work is the concern for a fair test, for a controlled experiment. Children seem to have an intuitive sense of what makes a fair test. What they lack is the ability to consider all the variables and the means to control the variables. It might be reasonable to consider a developmental continuum such as the following when thinking about control of variables:
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The first level of variables contains the simplest type: the nominal variable. Nominal variables have two or more unordered values: "This plant was watered; that plant was not." "This seed was placed in the sunlight and that one was placed in the dark."
- The second level of variables is the ordinal variables level. These variables have a sequential order and no determined intervals (for example, the sequential ordering of objects by relative weight).
- The third level of variables is the continuous variables level. These variables have sequence and equal intervals and are on a continuous scale: "This object has a temperature of 50 degrees Celsius and that object has a temperature of 57 degrees Celsius."
As students are asked to demonstrate their ability to do scientific investigations, it is important to keep in mind this sort of development in understanding and performance, not only with respect to the control of variables, but also regarding the other elements of doing science. The difficulty with the assessment may not be with the content, but with the level of variable embedded in the content.
Practical Reasoning
Practical reasoning about matters with scientific content (that is, the ability to apply one’s knowledge, thought, and action to real situations, not textbook problems) is influenced by the ability to (1) abstract and consider hypothetical experiences, (2) consider several factors simultaneously, (3) take a depersonalized view, and (4) realize the importance of practical reasoning and life experience. These factors develop throughout life.
One of the characteristics of young children is that they have difficulty dealing with multiple ideas simultaneously. With maturity and experience, they can consider several ideas at once and weigh benefits in relation to costs or risks. Their ability to abstract and consider hypothetical situations develops as students progress in science and learn to deal with more remote phenomena and generalizations.
As they mature, students also learn to take depersonalized views of situations and to consider other people’s points of view. Often, real-life problems involve not only theoretical and technical elements, but also personal preferences. What will be the social impact of a new waste disposal system? What will neighbors say if a traffic light is installed? How will other students react if lunchroom noise is diminished by staggering the lunch hour? To consider these questions carefully, it is necessary to understand different perspectives. The ability to understand the viewpoints of others increases with age and experience.
Young children also may not realize the need for scientific information in solving problems. For example, children below the age of 12 usually see no need to carry out measurements (Strang, 1990). Also, because young children have little responsibility for decisions affecting their lives, they may not see the need for practical reasoning. However, the more that students have done or seen, the more likely it is that they can solve real-world problems. With age and experience, the possibility increases that a new situation is analogous to a previous one and that the human, technical, and theoretical factors involved in a new situation have already been encountered.
All these factors suggest that practical reasoning should become a major factor in science assessment at grades 8 and 12 rather than at grade 4. As students become eager to take control of their lives, wish to try out their understanding of the world, and progress in development, practical situations related to their everyday life, school, and home provide excellent exemplars to demonstrate science-related practical reasoning. Thus, students might be asked to discuss problems such as noise abatement in the lunchroom, to design a simple apparatus such as a flashlight or a burglar alarm, or to plan a school garden.
By grade 12, students should be able to discuss larger science and technology-linked problems not directly related to their immediate experiences. Examples of these might be waste disposal, energy uses, air quality, water pollution, noise abatement, and the tradeoffs between the benefits and adverse consequences of various technologies.
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