I’m not sure about the A100 classes. I’m pretty sure it’s based on some secret fomula that no one actually knows because there’s never the right amount of officers for available jobs. Either too many or to few.
Back when I took the test, the essay was submitted when you filled out the written test application. Much easier than having to write it during the orals. IIRC, I had to write a pretend “reporting cable” on one of the role playing exercises.
There’s not really anything you can do to “prepare” for the orals so, if I were you, I’d take them and get them out of the way so you don’t start obsessing. It’s essentially a day of “what would you do if…” exercises, role playing and group “playing well with others” exercises. It’s designed to test your commons sense and decision making skills. Or at least it was back when I took it. Things to remember: wear a suit (and clean undies ); don’t be overly aggressive or arrogant; ask for opinions of your fellow examinees when doing group exercises; be polite; don’t make snap decisions; be confident; and always remember: the needs of the Service/Department always outweigh your personal needs.
The best thing I did to prepare? Valium.
It’s a long, emotionally/mentally grueling day. But remember - if you don’t pass, it’s not the end of the world. You can take the test again (and again and again). Well over half of my incoming class didn’t pass the orals on their first attempt. Having gone through them once gives one a decidely better chance the second go-round.