I am glad I didn't read this during high school. I think the main character's personal crisis about her education might have been a little unnerving at the time (though probably more so if I had read it after I had graduated from college and not yet found work), since as I read I identified in many respects with the main character and how she performed in high school and college.
I wonder if the "bell jar" she experienced was what we would think of today as a quarter-life crisis---a realization that all this stuff you've spent learning up to now is not how the real world works and much of the stuff you've learned you really can't apply in any meaningful way. I suppose, though that the quarter-life crisis rarely results (though could) in as extreme an action as a suicide attempt and a need to be committed.
Part of the main character's crisis may have been due to the limited opportunities for women as well. She seemed to have two options in her head: be a great writer or be a stay-at-home wife and only one was at all attractive. Once her confidence as a writer was broken there was only the wife option---to a boy she didn't much like, making the option even more unattractive. The bell jar may have been due more the loss of any other option rather than to any real "craziness" on her part.
From the post matter, much of this story was based on Plath's own experience as a young adult. She says in the book that she dreads the return of "the bell jar," which in real-life seemed to return for Plath based on her later suicide.
The narrative is very tight and believable resulting probably from Plath's intimate similarity to the main character. I like how it is told in first person, as it gives insight to why she is acting as she is. That is always fascinating to me, to see the rational side of an outwardly "crazy" person's behavior.
A very enjoyable read.