The increase in demand for college and career ready students has driven the need for education reform to ensure K-12 schools can support student learning across all content areas and grade levels. A STEM Certification process was established by the Georgia Department of Education as part of an effort to reform public school STEM education. Additionally, an international STEM Certification procedure developed by AdvancED has been implemented in several Georgia schools. As a significant component of STEM certification guidelines, problem based learning has been incorporated to stimulate student interest in science, facilitate self-regulation, and increase pedagogical and content knowledge. As Georgia schools become STEM certified, it is important to understand how certification has influenced achievement in math and science as well as important non-STEM disciplines such as English language arts and social studies. This causal comparative study examined if the STEM certification process altered student achievement in participating schools as compared to schools that have not participated. Student achievement was measured by the median growth percentiles (MGPs) between STEM certified and non-STEM schools in the content areas of English language arts, mathematics, science, and social studies at the fourth and fifth grade levels using a Mann-Whitney U test. The study found only the MGPs for fourth grade ELA were significantly higher (p = 0.004) in STEM certified schools. Overall, inconsistent differences in MGPs for ELA, math, science, and social studies were found between STEM certified and non-STEM schools.