Q. I want to make a video recording of a play/musical my students are doing in class. Is this within copyright?

Make sure you get permission from your students (or their parents if they are under 18 years old) to record the performance. You are within copyright to record the performance with the permissions, but you would not be able to distribute that recording without getting permissions from the copyright owner of the play. Once you distribute the play's recording you would no longer be within section 110.1 (classroom instruction) of the copyright law.