NSES Content Standard A 
Science as Inquiry: Abilities necessary to do scientific inquiry 
Grades 5-8, page 145 

Develop descriptions, explanations, predictions, and models using evidence. Students should base their explanation on what they observed, and as they develop cognitive skills, they should be able to differentiate explanation from description—providing causes for effects and establishing relationships based on evidence and logical argument. This standard requires a subject matter knowledge base so the students can effectively conduct investigations, because developing explanations establishes connections between the content of science and the contexts within which students develop new knowledge. 

Benchmark 1B The Nature of Science: Scientific Inquiry
Grades 6-8, page 12
Scientists differ greatly in what phenomena they study and how they go about their work. Although there is no fixed set of steps that all scientists follow, scientific investigations usually involve the collection of relevant evidence, the use of logical reasoning, and the application of imagination in devising hypotheses and explanations to make sense of the collected evidence.

Benchmark 1B The Nature of Science: Scientific Inquiry
Grades 9-12, page 13
Hypotheses are widely used in science for choosing what data to pay attention to and what additional data to seek, and for guiding the interpretation of the data (both new and previously available).

Benchmark 12A Habits of Mind: Values and Attitudes
Grades 3-5, page 286
Offer reasons for their findings and consider reasons suggested by others.

Benchmark 12C Habits of Mind: Manipulation and Observation
Grades 3-5, page 293
Keep a notebook that describes observations made, carefully distinguishes actual observations from ideas and speculations about what was observed, and is understandable weeks or months later.

Benchmark 12E Habits of Mind: Critical-Response Skills
Grades 3-5, page 299
Seek better reasons for believing something than "Everybody knows that . . ." or "I just know" and discount such reasons when given by others.

Benchmark 12E Habits of Mind: Critical-Response Skills
Grades 6-8, page 299
Notice and criticize the reasoning in arguments in which (1) fact and opinion are intermingled or the conclusions do not follow logically from the evidence given, (2) an analogy is not apt, (3) no mention is made of whether the control groups are very much like the experimental group, or (4) all members of a group (such as teenagers or chemists) are implied to have nearly identical characteristics that differ from those of other groups.