Its hard to say exactly what is so difficult about it, for some it may be the perception of the test. I think people talk it up a little, but grading can get tedious with real work experience-then the implicit and explicit direction for the LARE. Like Jason said I too (luckily) passed the first time but I do a ton of grading at work and it is in front of me all day on many projects. There is no question that it was a difficult test and I took every minute they gave to finish the exam. I literally was the last person in the room.
A couple of things I remember: The thing that got me pressured on the exam was time management-as others have said. To me, knowing where I was in the stream of time during the test really helped. Take a clock and time yourself on a simple vignette you haven’t seen before and you will see what I mean. Getting the concept quickly-since I do alot of grading, maybe that helped with some of the processing time it takes to get your mind wrapped around the problem. I cant really say other than to practice and keep practicing with the vignettes and made up problems. This may help you get a quicker feel for how grading works conceptually. I did not take a special prep class for the grading portion but I have heard those may be helpful in getting you tuned into the ‘LARE code’ requirements.
I remember that I only had real difficulty with one of the vignettes. Somehow I had transposed the grades for this vignette that just would not work and remember thinking “move on and come back to it.” That is what I did and I found the error immediately after coming back to it. After 4-5 hours straight your brain will be fried and you really have to start relying on your practicing of those vignettes. I think I was very tired and just got mixed up. It is an endurance test in some ways.
I hope you are successful when your time comes to pass the test. Knowing how to do grading “quick and clean” has been one of the main things to open doors for me with engineering offices and other LA’s for employment.