Nine years of results on 4.2 million of Indiana's Indiana Statewide Testing for Educational Progress (ISTEP) mathematics (math) exams (grades 3-10) taken after the implementation of No Child Left Behind have been used to determine gender gaps and their associated trends. Sociocultural factors were investigated by comparing math gender gaps and gap trends for (a) state public schools, (b) state nonpublic schools, (c) a low-performing metropolitan school, and (d) a high-performing suburban school. To control for changing sociocultural factors, multiregression analyses were conducted to predict grade-level (3-10) gender gaps and math scale scores using socioeconomic and ethnicity variables. The underrepresentation of females in earning advanced STEM degrees was investigated by determining the gender of the highest performer on the ISTEP math exams in grades 3-10 for each of state's 292 school corporations. Boys' percentages were higher across all grades by about a 2:1 ratio, similar to high-end results on Scholastic Aptitude Test (SAT) math exams. Simulations of distributions for d = 0.27 and variance ratio = 1.13 fitted 2013 college-bound SAT math empirical data. Results of the analyses of the state's ISTEP math exam data and the 2013 SAT math scores of college-bound seniors support the arguments that girls and young women possess the abilities to pursue STEM careers that require advanced mathematical skills.