Why is my child learning note-reading not by letter names like C-D-E but by solfege like Do-Re-Mi?

Because of the emphasis in singing and hearing in group lessons, solfege (do-re-mi) is easier to pronounce and more practical to sing in. Also, what the students learn is called “fixed-do” method, i.e. do=C, re=D, mi=E, etc, which is different from the “movable-do” method that is prevalent among pop music and singers.

The “fixed-do” method communicates the same name-to-note orientation as letter names. Students are actually learning the same thing with different syllables. In fact, letter names will be introduced later in the course as one of the subjects, which students must study and familiarize themselves with.