Trip
Although millions of people died in the Academy Domain, the Academy walls itself was bustling with happiness as the student walked around with a smiles on their faces.
The students were able to digest their gains from putting their lives on the line with no place to actually hide or run.
This was one of the advantages of fighting, improving after some battles, and gaining insight into your art skill or techniques.
Which further improves your combat power even if you don't increase your mana rank.
This is why battle maniac always improves faster than other people, simply because they bet their lives on the line to get where they actually are.
The students were also able to convert their demon corpse into points, and these were demons, not corpse of beast and monsters so the students got more points.