This is what my son was told at last year's SS regarding the CFA. As far as taking it at SS, if you pass it there you can use that score and don't have to take it again if you're satisfied with your score. However, if you don't pass it or if you think you can improve you score, you can practice and take it again with your certified PE teacher or coach. My son passed it there and didn't take it again and used the same score for USNA and USAFA.
I don't know which part of the country you are from but at last year's SS, my son said the hardest part for him was getting used to the humidity. Where we live we don't hardly ever have that kind of humidity, and he said he couldn't go to sleep at night even with all the windows open because it was so humid. During the cfa, he saw kids passing out and vomiting. He said he was surprised to see only about a 1/3 of them passed it in his group even though almost all of them were athletes.