It's fairly close to accurate, but there are several embellishments. Also keep in mind that it really focuses on her work on the UGRR and almost totally ignores her time as a Union spy. If you're going to use it as a teaching tool maybe you should have a discussion with your class about the way biopics are always somewhat dramatized and how editorial decisions are made that significantly impact the film. Also, keep in mind some parents might object to some of the language. You also might want to encourage your students to do additional research on their own. A good book for this is Catherine Clinton's Tubman bio, but for those more advanced students maybe Kate Clifford Larson's bio (though it reads more like a thesis).