I was warned, but didn't experiment, that dryer sheets leave a residue that will burn. Tale I was told says it is a low temp flame that won't bother you until someone notices and uses a fire extinguisher on you!
They were very strict on synthetics in the class I took. They say natural fabrics, wool or cotton, pull away as they burn (if they catch on fire), but synthetics not only catch more easily, they tend to melt into your skin making any burns much worse. (Again, I didn't experiment!)
Have fun in your class!
ETA: be careful with any exposed skin with any arc welding. I had a tiny sliver of flesh exposed below my hood above my shirt and jacket in my first class. I got a wicked "sun" burn there.