How can I share a student's work with the rest of the class?

Press the Lecture mode button.
Press the Play tab from the row of tabs at the bottom of the screen.
Press a student number, corresponding to where a student is sitting in the classroom, to bring students into the lecture. When a student has been brought into the lecture, their instruments and mic are enabled, if student mics are enabled in class preferences (this is the default setting). You and the class will be able to hear that student's mic and instrument. A microphone appears next to the student's name to indicate that they have been brought into the lecture.