  "Rigor" is an often sought after but ill-defined concept in education. This
work reviews several models of rigor from current literature before proposing a
tool which is used to analyze science education throughout history. The
20\textsuperscript{th} century science education in the United States was
subject to changing sociopolitical motivations about the use of science both in
general and for students. These factors as well as developments in theory of
learning and broad education reforms had changing affects on the level of rigor
in science education. This work analyzes the theoretical level of rigor of
science education in the US based on two main motivating factors for science
education; science as a social endeavor and science as a discipline, throughout
the 20\textsuperscript{th} century.
