The PSAT 9/10 is a standardized test that is administered to freshmen and sophomores in April. This is great practice for the SAT.
The SAT is administered to juniors in April. This is a college entrance exam, as well as WHS graduation requirement.
The ACT is another college entrance exam. This is not required, however, can be taken independently on a national testing date.
The PSAT/NMSQT is available for juniors administered in October. This is not a required exam.