I was pleasently surprised by how tense this game made me feel. I'd chalk it up to some nice scene-setting, good use of sound an a format that tightly controls what can and cannot be known by the player (the text boxes gave nothing away). You did a nice job ramping up the tension slowly, as well as giving each student a distinct personality through what they said and did. I felt a real impression of being a cover teacher for kids I don't know all that well. I also had a moment while playing when I had to stop and think about how I felt regarding dissection. It's not something I did in school and I find myself on the fence about it. I think this was a very smart decision in terms of setting things up with a general uneasiness.
The only thing to mention that was out of place was a couple of lines I read had repeated words/grammar issues which somewhat took tension away, but this is a very small thing.
Really nice job! :)