Hello!
I cannot tell anything about the fail rate baceuse it is totally relative. I mean there is a limit against your knowledge and skill. If you are above this line, than everything is ok, and you will finish the course.
There were courses when everybody was above the line and everybody finished the course succesfully, but of course there are always some excemptions. I can say that this 90% fail rate is bull****. The course is not going to be an easy job, but with huge effort you can perform well.