The purpose of this research is to investigate the impact of international assessments on mathematics teacher development in the Kingdom of Saudi Arabia. The Ministry of Education in KSA is committed to providing high-quality education, but most students score below the international average. Preliminary research on performance in KSA indicates that most students record low scores in the mathematics subject. Also, the recent Trends in International Mathematics and Science Study (TIMSS) scores published in 2015 categorize KSA among the five countries with the lowest average achievement in mathematics around the world. The current study examines the factors contributing to low TIMSS scores in mathematics and evaluates how these scores can be used to enhance teaching recommendations. Surveys were used to collect data from mathematics and science teachers in Saudi Arabia. Based on the responses received from the study participants, this research finds that teachers have a high understanding of the school curriculum and the required strategies for implementation. Most of the study subjects also rated school leadership’s support for teachers’ professional development to be low in KSA. The results also note some aspects of teacher development that need to be improved, such as job satisfaction for teachers in school, the students’ ability to achieve academic school goals, as well as students desire to do good work at school. Two independent samples t-test were performed to determine whether there are significant differences in teachers’ development and performance among math and science teachers. The findings of the t-test revealed p-values < 0.05. There were no significant differences in the implementation of the school curriculum and the use of activity books in the classroom between mathematics and science teachers. However, the means reported by mathematics teachers were slightly higher compared to those of science teachers. A correlation analysis was also performed, and the results revealed a significant positive relationship between teachers’ expectations for student achievement and teachers’ ability to inspire students (r=0.515). The analysis also revealed a significant positive relationship between students’ ability to achieve academic goals and their desire to do good work at school (r=0.638). Lastly, there was a significant positive relationship between school and teachers’ cooperation to plan education and leadership support for teachers’ professional development (r=0.585).