Teacher needs to wake up. This isn't some just some slight mishap happening on some field trip or something. They're in a completely different world, with no proper understanding of how to get back, and in a very dog eat dog kind of world. You think you're going to bring everyone back safely, think again. Especially when some of them turn out too far gone to even really save, or risk keeping around. Sensei's foolish optimism is what will get the entire class killed if she's stupid enough.