It tests private-pilot level knowledge and competence. You take a short written exam, then do some very basic stuff in the simulator. If you are current and look over the PPL written test prep book again, you will be fine.
I have heard and read almost nothing bad about ATP in this forum and from others and I had put ATP at the top of my list. When I made a call to schedule a tour I was told some information would be sent to me in the mail and after I looked it over I could call to make an appointment for an interview which, included a written evaluation and a simulator evaluation which would cost me $100.00. Is this standard practice when touring these larger flight schools? I also arranged a tour at Flight Safety over the same trip and they made no mention of an interview fee. I can’t imagine how bad somebody must perform for them to turn down the 35 grand they would take in, but beside that I am a little put off by the $100 “interview” fee. After all who is interviewing whom here? Maybe I am missing something here but I would like to actually take the tour and see with my own eyes what I am investing in before I plunk down the $100 interview fee.