AP tests are harder, which is why the elite schools only take AP and not CLEP or any of the rest. If you don't take AP tests while in high school, you have no practical chance of taking them later. The exception might be a high school, probably a private one, that would let you take the test along with their students in May.
One of the reasons AP tests are harder is that they aren't just multiple choice. They take longer and include written and other types of responses that are graded by humans. You do not have to be enrolled in AP courses to be allowed to take AP exams, although some high schools impose that restriction on their own. Most students who take AP tests are in AP courses. But students not in AP courses often do just fine on the AP tests.
There are AP tests for which there is no CLEP equivalent, such as physics for science majors, which is a different physics than the one covered in the CLEP Natural Sciences test. It is important to pick the correct AP test. English Language and Literature vs. English Language and Composition, for example. Different universities prefer one over the other. Those two tests are generally more accepted than CLEP College Composition.
Some AP students probably have placed out of two years of college, although it would be very few. It could be done by earning credits as follows:
year one
biology
calculus
chemistry
English
physics
year two
art history
Chinese, French, German, or Spanish
macroeconomics and microeconomics
U. S. History
studio art: drawing or world history
If you have an associate's degree by the time you graduate from high school, you probably don't need to take the ACT or SAT. But that depends on where and exactly when you apply. Generally if you have 30 semester hours of college credits, you don't need ACT or SAT scores. However, some schools make a distinction between hours from actual courses vs. credit by examination.
Take all of the AP tests you have a reasonable expectation of passing.
One of the reasons AP tests are harder is that they aren't just multiple choice. They take longer and include written and other types of responses that are graded by humans. You do not have to be enrolled in AP courses to be allowed to take AP exams, although some high schools impose that restriction on their own. Most students who take AP tests are in AP courses. But students not in AP courses often do just fine on the AP tests.
There are AP tests for which there is no CLEP equivalent, such as physics for science majors, which is a different physics than the one covered in the CLEP Natural Sciences test. It is important to pick the correct AP test. English Language and Literature vs. English Language and Composition, for example. Different universities prefer one over the other. Those two tests are generally more accepted than CLEP College Composition.
Some AP students probably have placed out of two years of college, although it would be very few. It could be done by earning credits as follows:
year one
biology
calculus
chemistry
English
physics
year two
art history
Chinese, French, German, or Spanish
macroeconomics and microeconomics
U. S. History
studio art: drawing or world history
If you have an associate's degree by the time you graduate from high school, you probably don't need to take the ACT or SAT. But that depends on where and exactly when you apply. Generally if you have 30 semester hours of college credits, you don't need ACT or SAT scores. However, some schools make a distinction between hours from actual courses vs. credit by examination.
Take all of the AP tests you have a reasonable expectation of passing.
63 CLEP Sociology
75 CLEP U.S. History II
63 CLEP College Algebra
70 CLEP Analyzing and Interpreting Literature
68 DSST Technical Writing
72 CLEP U.S. History I
77 CLEP College Mathematics
470 DSST Statistics
53 CLEP College Composition
73 CLEP Biology
54 CLEP Chemistry
77 CLEP Information Systems and Computer Applications
75 CLEP U.S. History II
63 CLEP College Algebra
70 CLEP Analyzing and Interpreting Literature
68 DSST Technical Writing
72 CLEP U.S. History I
77 CLEP College Mathematics
470 DSST Statistics
53 CLEP College Composition
73 CLEP Biology
54 CLEP Chemistry
77 CLEP Information Systems and Computer Applications