Collective punishment
The line of buses didn't exit the city, as Nero had been expecting, but instead took them to a military base within the city, attached to the southern boundary wall. Since this entire area was a restricted military zone, it was actually Nero's first time coming here.
He observed everything, memorising the layout as they passed by, taking note of the various buildings they passed and the arrangement of the various barriers. By now, this was second nature to him, and it was not something he needed to do consciously.
That was also why, as they arrived at the exact facility they were heading towards, Nero was the first person to notice that the number of buses was a lot more than it should have been. The extra vehicles were probably from the other schools around the city. It seemed they were gathering all the students who could possibly meet their needs.