Let me start by saying that I loved the concept of this movie, and the way in which they tried to bring this classic thought experiment to life. However, from both a philosophical and filmmaking perspective, the execution of this story was hugely problematic.
I am writing this review as someone who has been a passionate reader, student and teacher of philosophy for many years - and as someone who still regularly uses this very thought experiment as an educational tool.
1. At one pivotal point in the movie we are told that philosophy is not morality.
Not only is much of philosophy dedicated to questions of morality, but this entire film is built on a thought experiment that was created to endorse a particular moral philosophy - that of utilitarianism (consequentialism in particular). Such a basic and fundamental error of fact is absolutely unforgivable in a movie that is supposed to be all about philosophy.
2. The final iteration of the thought experiment is meant to show us that utilitarianism is a flawed moral philosophy, and that there are other ways of responding to the scenario it has set up.
However, our main protagonist is still using the moral philosophy of utilitarianism when she executes her new, and supposedly non utilitarian solution to the crisis - the only difference between what she does in the final round, and what the group did in the previous two rounds, is that she makes judgments about the worth of people and chooses them based on traits she deems to be of value rather than the trials that the class formerly deemed to be of value.
The key point though, is that she has still judged people's value based merely on the attributes they posses.
3. The group suicide at the end of the third solution to the thought experiment is not only more like homicide (in that she is the one who decides that everyone else will die), but it is also, once again, utilitarian in nature.
She has deemed that their life no longer has value based solely on the fact that they do not posses the necessary functions for rebuilding their brave new world (which is, ironically, exactly what the teacher was trying to get them to do the first two times, and exactly what she was supposedly avoiding with her third and final solution to the problem).
From a filmmaking perspective; the suicide bomb was also a very weird and contrived way to achieve that plot point - it was an event that completely violated the very rules which the film had created for itself up until that point.
It's one thing to completely change the parameters of the thought experiment as you go (to suit the plot development), it's another thing altogether to start conjuring up fantasy outcomes - an action which was not previously allowed/possible.
If she can conjure up a bomb for convenience, then why wouldn't she conjure up a life- saving text book, or a washed up (and functional) escape vessel instead?!
4. The 'thought experiment inside the thought experiment' that we had presented to us in the third and final round was:
a) completely out of tone with the entire rest of the film (it suddenly goes from dramatic thriller to an American Pie style slapstick comedy).
b) not actually a thought experiment at all - instead it was merely a sexual fantasy (thought experiments involve scenarios that are meant to be philosophically pondered and possibly solved - but what we saw was neither).
5. The remembering of the code in the third and final round of the thought experiment, by spying on the teacher at the end of the second round, was a complete violation of the laws of the universe the film had created (as well as a violation of how thought experiments work).
Even if you change or add to the parameters of a thought experiment in subsequent variations of it, what you are effectively doing with this action is creating a brand new thought experiment to be pondered and debated.
It's effectively a reset, where everything goes back to the beginning, except this time some of the fundamental parameters have changed so that different logical arguments are brought into play.
But having a character do something like steal a code from a previous discussion of the thought experiment, and then use it in a brand new discussion of a band new version, is nonsense at both a philosophy and filmmaking level - if she has the code, why is she also suddenly alive again when, at the end of the previous thought experiment she was killed in the process of acquiring the code.
6. The ending of the movie is terrible, and it really deflates what has been a solid effort at filmmaking up until that point.
a. We, the audience, despite not having been given any reason to do so, are suddenly expected to care about a creepy (and almost certainly illegal) affair that the teacher is having with a much younger student.
b. The nature of the character of the lead female suddenly undergoes a totally inexplicable 180 degree change, for no good reason, just so that a contrived ending can be executed
c. She ends by stating: "you are a very good teacher Eric", despite the fact that he is sleeping with students, has just been caught trying to publicly humiliate a male student he is jealous of, and has just finished threatening to strip her of the A+ grade she has earned simply because she refuses to join him in humiliating the male student he is jealous of. (And that's not even discussing the fact that he gave a female student he was sleeping with an A+ grade in the first place!)