Sounds like a great class.
On the subject of speed, rpms have to be considered relative to diameter. There is a rule of thumb stating that rpms x diameter in inches should be 6000-9000. It's not written in stone, but it's a useful reference. At the upper end (rpms x D = 9000) the rim speed is about 27 miles per hour. The more mass and the higher the rim speed, the more energy is embodied in the spinning wood and the more damage it can do if something breaks loose.
You probably know all this, and everyone can make their own judgments about shop safety. My tolerance for getting hit by speeding objects is pretty low. I tend to regulate the speed by perceptible vibration and adjust my tool feed rate to match.
I was showing my friend how to use his McNaughton coring system on a 8.5" walnut bowl blank last Monday. It looked quite sound to me. He called me later that day to say he had blown the piece up at 1700 rpm, about 2/3 faster than I would have spun it. He's getting to be a good turner, but he's only been doing it for a year, usually wears only safety glasses, and had never heard of my rule of thumb. I worry that he is going to get beaned one day.
