A Teacher takes the gasp-awe taboo of teacher-student romance and puts it on center stage. Conceptually, A Teacher is highly engaging and has a lot to say. Unfortunately, the execution of those ideas never gets off the ground.
The viewer is flung right into the fray. Diana, an AP English teacher at a public high school, is already in the throes of a relationship with student Eric. While the movie never specifies how long they've been together, it can be assumed that the relationship is already sexual before the camera captures anything. On the one hand, this allows us to see the relationship for what it is at the outset, without our perspective getting colored by knowing characters (and yelling at them for bad mistakes, etc). But the trade-off is that we are flung into this scenario without any emotional attachment. And the movie never tries to bring us up to speed. It's like a kid relating a story: "And then we got into my SUV. And then we had sex in the back seat. And then we cuddled. And then he left. And then I missed him. And then I texted him. And then he texted me back."
They story gets conveyed, but it is always holding the viewer out at arms length. We see the effects on both Diana and Eric, but without any kind of glimpse into their mind to help lead us along. Sure, some if it can be assumed. Eric is a teenager. He's liking the sex. He's liking having a relationship. Perhaps he likes the weird power exchange, something he seems to drink up in one weird scene where he wants to get physical and Diana doesn't.
But to an extent Eric feels like a secondary character. He's The Romantic Interest, but the focus is almost entirely on Diana. And she is a tough cookie to crack. There are a lot of interesting surrounding details that seem to point at issues in her life, but none of them are explained. There is an interaction she has with her brother that hints at family troubles, but there's never any resolution there. There is her general inability to fit in with her peers--she's a fish out of water at a party, for example. Her feels like a cog that doesn't want to fit anywhere. Nowhere in this life machine seems to provide a comfortable slot for Diana. So maybe that's what the relationship is; a place she feels she can put her cog. But the weird thing is that even that fails to fit her. Her existence outside of work is either having sex with Eric or sitting around her apartment by herself, scrolling through Eric's Facebook photos. Again, larger issue being pointed to.
Some of this happens in the latter part of the movie where she seems to go crazy. In fact, Eric says that at one point. But her actions feel less like craziness and more like addiction desperation. Put her next to a junkie trying to get a fix and there's very little difference. In fact, replace Eric with a needle and you could make a very similar movie.
And if the movie had been able to bring all of these disparate issues into focus to provide a reason for her relationship or some sort of psychological viewpoint we could see or understand, A Teacher could have been an astounding movie. Answer the questions of why she acts like an addict in this relationship. Why is her family reaching out to her, but she's running from them. Why, why, why! But none of these things get touched on with any kind of resolution. Nothing happens to make us say, "Oh, Diana makes sense now!". Instead they just exist as glimmering fools gold; half-baked ideas that are meaningless.
And without this psychological understanding of Diana, all we as a viewer is left with is what the movie gives us: a story of a relationship that keeps the viewer at arms length until the end.