I'm another fan of the cheap Brothers for classes. One of the nice thing about (most) Brothers is the feet are interchangeable. They are basic and easy to use, even low end ones have threading assists.
My first one lasted for around 7 years of pretty heavy use and hard treatment. Started having issues with the bobbin casing. It was the Costco machine from that time, here's the current offer from them:
https://www.costco.com/Brother-XR334...100421876.html
My current portable Brother is super low end, got it at the thrift store for something like $20. It is a Brother 2230 and it is just fine for classes, does everything I want. Happens this machine (maybe why it was in the thrift store) had issues with the bobbin winder, so I bought a portable one and everything is just fine.
The downside of the 2230 is it does not have an integrated case, I carry it in the box. The previous one had an integrated case that fit over the machine with a hand opening, that was better than nothing but if I was going to go to a lot of classes, I'd be looking for a case with some sort of locking/shutting function.