Here is a little treasure. It is Sister Mary Antonine Goodchild's Gregorian Chant for Church and School (1941). It's like the fast track to chant, just a few early chapters on the basics and then you plunge right into the repertory, and all the main settings and hymns are here, one by one, in Solesmes-style notation. It has translations. It even has study questions! Fr. Samuel Weber is the one who told me about this. He remembers it fondly.
I've thought for a long time that a book like this needs to be written. Well, it's already been done. If I were founding a schola today, or teaching middle school kids chant, this is the book I would use. No question.