Hello, I have a question regarding grades and all that Jazz.?

Okay, so apparently we get progress reports in between semesters, and while doing so they tell us your grads and with it a warning wether or not you may fail at the semester, I had a B in a class and did not get one of these warnings and ended up pulling out an F, and without her giving me that warning I ended up passing the class due to that, does that work for everyone, or is it a one time thing?