Bizzi_Boi,
I am aware that it is not uncommon for one student per class (a class is up to 16 students, and sometimes it is more than one) to fail or drop out.
Obviously this doesn't happen in EVERY class, but I would say it is at least 3 classes out of 4 where it does.
I am sure that operating crew can think of many people they know who decided that the job wasn't for them within the first 12 months or who didn't make it through the training school for whatever reason.
Feel free to PM me if you require more details.
SG