my favorite vintage heavy machines with a few stitches.... Morse! I have a fotomatic IV, and a fotomatic III. The III is simpler and has no plastic gear; the IV has one plastic gear and is slightly more temperamental(at least for my 2 machines).
Of the singers, I prefer the 503 over the 500- just a personal preference as I hate trying to maintain/repair the cam stack if it breaks. I would much rather have a single disk that breaks and can be replaced. However the top cover is fragile- which is fine if only an adult is using it.
there are a fair amount of japanese mid century machines that had 3-4 stitches... brother, morse, capri, new home, remington, etc.
and for taking to class? I adore my little kenmore 158.1040.