......and you would be correct in your assumption. However, CS5.5 and CS6 are, I believe.
Just watch your step if you download & install CS6: if you don't follow the instructions for it AND the update (which you must do immediately, I understand) TO THE LETTER, you can cause yourself some major headaches. With CS6, it sounds like knowing what you're going to do before you do it would be the order of the day.
Thank you, Dave!
After Effects CS6 and CC are the only versions supported on Mavericks.
See this page for crucial updates: