I personally disagree here rather. If one thinks the game as a story in a 3-act-structure (
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), one could see the end of chapter 2 as mid point of the story. The introduction of Zoe and a possible cliff-hanger with an event, in which Zoe can show her impact to its fullest would make this in my eyes perfect.
But I must confess, that the impact and possibility of this outcome will depend on what Zoe will finally be. I hope that Zoe's rather a manipulative person who can also see the weaknesses of the students and use them to her own advantage than one that is acting herself. Thus the headmaster should not be able to punish her initially, because there is no evidence, that she is behind anything, basically a mirror of his own personality. Under this circumstances, this scenario would work very well. But I'm not sure, what she will actual plan is.
To make this nevertheless positive, one could let behind the headmaster initially thinking but gradually smiling, when he acknowledges a hypothesis about the key to Zoe's teaching but not show what it is to the player at the end of chapter 2. Zoe's weakness should be slowly revealed to the player in chapter 3, when the headmaster gets more and more evidence for his hypothesis about Zoe and starts to set traps.