I hate to sound cruel but if your friend could not pass while riding on a little 250, he probably just shouldn't be riding anything on two wheels with a motor; not even a Vespa.
As you now know, I've been riding a LONG time and back when I got my license there was no such thing as the riding course so I had to learn on the street one week then took my test the next. It's really not that hard but I also think you have to have a certain personality for it.
I too, have a friend who took the course and passed with flying colors. She's all of 5-foot 1, weighing in just over 100lbs! I think it's worth it, not only for the education, but when you pass, you get your license. One-stop shopping eliminates the need to do a separate test at the DMV; which in itself is worthwhile.
Riding on two wheels simply isn't for everyone. I ride, my dad rides and one of my brothers rides. My other brother tried from peer pressure and literally hit a wall his first time out. He hasn't ridden since, realizing it's simply not his thing.
OK, I think I got off-topic but you also have my answer. In general, the course is good for those who have no other learning option. Maybe the instructors weren't great or maybe your friend simply doesn't have it what it takes, despite his desire.