I touched on CLEP exams some time back as my hope was that my son would put a ton of college credits behind him before graduating. But Alas, that did not happen. He did get 6 English credits that the college he is going to will accept, and plans take one more in math before the end of this school year. Maybe he will even attempt one of the two tests he did not pass last time. But in the end, he is the type that needs to actually sit through the class to pass it, so his CLEP success has been limited.
Let's face it CLEP exams are HARD. It is a college level test, so there is no shame in not passing it when you are only 15 or 16 years old. There may be shame in not trying though. For us, even when he did not pass, it was a learning experience in figuring out his strengths and learning how to study. Studying for the tests have also given him the exposure needed to pass the classes in college when he takes them formally.
Next year, my daughter plans to spend her entire senior year taking CLEP exams (she failed one as a high school Freshman and hasn't wanted to take one again) Now she plans to take at least 4. I feel like she will have an easier time as she just barely missed the one she did fail, and now she is older and more mature.
One important thing to remember is that CLEP is not for everyone. Students should look at the colleges they hope to attend to make sure that CLEP exams will be accepted. If they aren't, you can still take a few CLEPs to prove your worth, but you may have better success getting AP tests or SATIIs accepted for college credit.
Read: Homeschool Questions and Answers: AP and CLEP Exams
How to Study for the Analyzing and Interpreting Literature CLEP