I was put on a Performance Improvement Plan on my 10th day at the company after "not meeting expectations" at the end of the Academy (intensive training program to learn how to use Appian's platform). No face-to-face discussion beforehand, just a meeting scheduled with my manager's manager & an HR rep. They told me my project didn't meet all the requirements, my quiz scores were too low (the instructor explicitly said they were just for learning & didn't matter, and I got a 93 on the comprehensive final), and because I was late to Academy.
I could talk about mitigating factors like how I had the flu during Academy, but does it really matter? I don't really think anyone should be put on a PIP that soon. Give them at least 2 months to get a full assessment of their strengths and weaknesses. I was on a PIP the day I met my team & got my own desk.
Obviously I quit shortly after. There were 6 people in my Academy group and I wasn't even the only one to quit within their first 6 weeks, so that should tell you something. If you look through the other reviews, there's another employee who was let go on the spot after Academy.