Consider wearing a loose jacket and fix the earphones within the jacket and down in your sleeves. Here, you should make sure that the earphones remain a bit inside the cuffs.
Put your MP3 in your pants’ pocket and keep the volume low, as you will never want your teacher to catch you just by listening to the sound of the loud music coming out of the earphones. Place your wrist near your ear and your will be able to hear the music, without even get noticed.
The other way around is to roll the earphones over your MP3 player and hold it in your hands. You can then slide your hand slightly in your jacket’s sleeves and lean you head on your hand. This way, you can make your teacher feel that you are just leaning your head as if you are a bit tired.
You can also purchase a Bluetooth headset and cover it using a cap or even with your hair. Here, you should make sure that your Bluetooth device is not set to discoverable, as your teacher can catch you if they find any Bluetooth device, using their laptop, active in class.
You can also wear a hat and place your MP3 player inside it. Just take out the earpiece and cover it using your hair. You can also hide the earpiece by just wearing a cap with ear flaps.
Wearing a hoodie with the hood up is another great way of hiding your earphones from being detected by your teacher. Keep your MP3 player in your pants’ pocket and run the cord through your hoodie, to your ears. Here, you should try to run the cord from behind the ears, as this will also hide the earphones from anyone standing in front of you.