How can I exclude students from lecture mode so they can work independently?

Press the Lecture mode button.
Press the Setup tab from the row of tabs at the bottom of the screen.
Press the number corresponding to where a student is sitting in the classroom, to bring up the QWERTY Keypad.
Press Omit from Lecture to select it. If checked, the student will not be able to hear your mic or instrument. This is ideal if one or multiple students are working outside of the rest of the class. An X will appear on the Play and Setup tabs in the group box to indicate that this student or group box is omitted from the lecture.