When humans are given ultimate freedom, with no constraints or morals, their true nature is revealed. And when placed in a do-or-die situation, survival instincts take over. This was the exact situation in the arena.
The children instinctively knew who the strongest among them was: Nick Vintal, the black horse with a near-certain chance of winning. As soon as the word "start" was heard, four of the kids moved to the opposite side, except for Renault. He stood in a corner on the right, arms crossed, as if what was happening didn't involve him at all. It seemed like some of his teacher Bowen's demeanor had rubbed off on him. Anyway, Renault was already extremely narcissistic.
The other three exchanged glances and came to a silent agreement to attack Nick together. It seemed like Renault was out of it so they started to attack first.