The movie follows the course of an unmarried teacher's life and loves over the period of her lengthy career.
The narrative has to cover a fifty-year span in 90-minutes, which is a challenge even for the best screenplays. This one, however, cobbles together both people and events in a loose way that unfortunately gets little beyond surfaces. Other reviewers are correct—there is very little character development. Instead, people more or less drift in and out of the teacher's life without time to develop. As a result, it's hard to engage with characters, and even with Scott's Miss Bishop since the teacher's role is underplayed. (An exception, as others note, is Minna whose difficulty is very vividly done.) Still, Miss Bishop's recessive manner perhaps conveys repressed emotion, not improbable behavior for a spinster of that time. If some such were intended, it would be an interesting angle, but I don't see much thematic evidence of that. All in all, Miss Bishop comes across more like an on-looker to her own life rather than a participant.
Nonetheless, the film deals, at least tangentially, with a difficult topic for the period. That is, can an unmarried professional woman have a rewarding life without being a wife and a mother. To the film's credit, it appears to say yes, as the final tribute scene affirms. Still, the film does fudge by making the spinster (Scott) attractive and with a life-long suitor (Gargan) whom she inexplicably keeps on a tether. So, remaining unmarried stands as her choice rather than an outside imposition. The film would have been more memorable, I think, had production made Miss Bishop more plain, and dealt with the problems of a plain, unmarried woman given the mores of passing generations. But dealing honestly with plain women was never a Hollywood or box-office favorite.
Anyway, the movie's mainly a sanitized concoction for viewers who like dipping into old style Hollywood soaps. The production's not without its moments, but the overall effect is pretty loose and sticky.