The SAT and ACT are the primary standardized tests colleges use to assess student learning and achievement. Some schools accept only one test, while others allow students to choose the test they want to take. If you score poorly on one test, taking the other test might be an opportunity to raise your scores and your college admissions chances. Check with your school to find out whether they take the highest test score or average all your scores.
If you take Advanced Placement classes, you often can get college credits if you pass the AP exam. Although you can take these tests after you start college, taking them before you register can help you choose the right classes and estimate the time it will take you to graduate. Some schools offer AP testing as part of AP classes, but other schools require that students independently register for the tests.
Some schools require placement exams to ensure that you enroll in the right classes. Placement exams are particularly common for math, writing and English. Studying for the test in advance can help ensure that you don't end up in remedial classes. The studying also prepares you for the academic rigors of college.
Some states require that high school students take a graduation test before they can receive a diploma. If you fail the test, you might be able to retake it or take only the portions you fail. In Alabama, for example, schools are required to offer remedial training to students who fail the test on the first try. Even if you get into school, you won't be able to graduate and attend until you pass your high school exit examination.