NSES Content Standard G 
History and Nature of Science: Science as a human endeavor
Grades K-4, page 141

Although men and women using scientific inquiry have learned much about the objects, events, and phenomena in nature, much more remains to be understood. Science will never be finished.
 

 
The most closely related benchmark is at a higher level of sophistication.

Benchmark 1A The Nature of Science: The Scientific World View
Grades 9-12, page 8
No matter how well one theory fits observations, a new theory might fit them just as well or better, or might fit a wider range of observations. In science, the testing, revising, and occasional discarding of theories, new and old, never ends. This ongoing process leads to an increasingly better understanding of how things work in the world but not to absolute truth. Evidence for the value of this approach is given by the improving ability of scientists to offer reliable explanations and make accurate predictions.