I had some electronics projects to do, so last night our kitchen became a lab.
For my centres, I got a small amp for $5 that has bluetooth and it's the size of a pack of cards. It's pretty loud, and will allow me to play music in class off my phone without plugging in.
I also salvaged a mini mixer from an old powered speaker that wasn't working, saving me $20.
You may appreciate the nails I used while testing things.