Few studies have analyzed the effect of the drivers of school performance over time. This research investigates how school-level student characteristics, such as funding and student-teacher ratio, influence school academic performance in the short-term and in long-term, a key differentiating feature of this work from other studies. Our focus is on the U.S. state of Georgia, but the setting of Georgia is the same as settings throughout the U.S.: considerable variation between schools in achievement and resources. In this study, school performance is defined as the proportion of students that meet or exceed benchmarks on end of year exams. Study findings indicate that teacher experience, measured by average number of years teaching, and student-teacher ratio exhibit the largest effect in both the short and long-term. Poverty rate exhibited a strong negative effect on school performance, confirming previous studies. However, poverty rate had the most impact in the STEM subjects of math and science. School funding did not show any significant effect in school performance in the short-term, but a significant positive effect in the long-term, such that increased school funding per pupil improved school performance in future years. Our results indicate that investing resources to increase the number of teachers and hiring teachers with more experience can be economically more effective than simply increasing the per-pupil spending, at least in the short-term.