I think my EMT class did an adequate job of preparing me for both the NREMT and the real world. An EMTs scope is extremely limited anyway, and like anything, the real world is different from the classroom, so there are obviously some things you just have to learn by trial and error, but the important things were covered in EMT class for the most part.
EMT classes vary greatly though, I had a laid back paramedic instructor who had a relaxed teaching atmosphere, and the students in my class tended to be older and more mature than many classes, and we helped each other out, so we had a really great class and everyone passed the NREMT first time, and most of them are either medics now, or just volunteered in EMS while keeping their day jobs(like me).
By contrast I helped out with some skill stations prep for a different school that was much more strict, they had almost all kids right out of high school or in their early 20s, and many of these spoiled brats needed the discipline and structure. They tended to snicker and belittle other students who struggled, it was like a lord of the flies atmosphere. As a result I think the instructors had a really tough time teaching them and they had a lot of failures. I dont know how many passed or failed the NREMT, but I imagine more than a few failed, and I dont think I would recommend a single student from that class for an EMT position.