Hey Guys listen it's just a show what you know test really, nothing else really, she just wants to see if the students are confident and skilled enough to kill dummies that won't move, that's just it, but there will come a time where the training will be harder than just stab a dummy several times. 

Also talking to the dummies doesn't count as taking care of the dummies, where here to attack the dummies, not talk to them. 

Also there is an army of dummies, Sayaka didn't burn all of them to the ground, there are still many that can be cut shot or blown up.