The duels sounded great to all of those in the lower classes but they have to be careful due to the rules that the school had put in place for them. There is a sense of strategy now because each person only has one shot to challenge someone for the entire year if they lose. The biggest thing for most will be learning to exploit people's weaknesses and also find the said weakness.
For example, someone that has an ability that involves fire would more than likely not want to go against the girl with the ocean hair sitting in the back row because their ability will not have a strong effect and make it harder on themselves. What they should do is find someone that has an ability for example plants or some sort of flammable material. This would make it a lot easier for them to win and move up the ranks.