Samantha is a principal at an elementary school. Three years…

Samantha is a principal at an elementary school. Three years ago, the school implemented a new curriculum to improve state test scores. Samantha gathered data from students during these three years from her school and from a school that did not implement this curriculum. She plans to compare the students state test scores across the three years from her school to the other school. This was an example of which type of study design?