Sign in with your school Google account to record.
Put the headset on. Tap each button and say whether the sound comes from the headphones or from the iPad's own speaker.
Scratch the side of the microphone with a fingernail, then read a line out loud. The bar should jump.
This is the test that matters. Read out loud normally for three seconds, then do it again with a finger held over the headset microphone. If covering it changes nothing, the iPad is listening to the room instead of the headset.
Sends the microphone straight to the headphones so you can hear what is being picked up.
The same path a real recording takes. If this sounds like the room rather than the reader, the headset microphone is not being used.