The students are given quite the shock to learn that the government had a full plan for killing Koro-sensei. A smart plan tries to take him by surprise; if not, you would trap him. At this point the students just feel helpless in what they can do.
What is shown well here is how adults can treat kids as kids. Many times they will take action without thinking about what the kids feel about the matter. It is more what they feel is the right thing, even if the kids wouldn’t agree. We see this as they put the blame on Koro-sensei, where now the kids have many sympathizers, but it was based on lies. Many times adults can think they are doing something for kids/students, but really they are doing it for themselves. Actually, the government utilizing that to their advantage is even worse. Of course, their argument is that Koro-sensei has only less than a 1% chance of blowing up, but you can’t blame the adults for looking at the worst-case scenario considering what happens in that worst-case scenario.
It’s good that Irina and Karasuma put trust in their students. After all, both of them are powerless here. While it would be tricky for the kids to pull it off, at least the plan is feasible. Which they can get working. Asking for help, regardless of who it is, is a sign of being a professional, as Karasuma has stated that being is important.
Makes sense in the mountains surrounding the school; the students would be at a strong advantage. As they take care of the mercenary group. Though them even being able to deal with Hojo as efficiently as they do feels like they overhyped Hojo’s skills. Of course, one man can only do so much, but he should have been more prepared since he should have been knowledgeable enough to get away from a disadvantage point.