Remember that as Sophomores and Juniors you should be signing up to take the PSAT - which is given in October at our school every year. Look for sign-ups in the career center begining September 15th.
Juniors should be registering to take either the SAT or the ACT your Junior year. We like to suggest that you wait until the end of your Junior year so you gain as much knowledge as possible.
As Seniors you can take the test through the December test date. Most Colleges and Universities will not accept any scores after the December test date (for Seniors).