There were (at least) two rimmed versions of the .236/6mm.

One, a fatter cased version was known as the .236 Remington Sporting, and is quite rare.

The .236 Navy rimmed was - I believe - one of the chamberings in the M1899 bolt-action.

The teacher mentioned must have been Frank Wheeler. I corresponded a bit with Graham Burnside, another early writer and cartridge collector when I was in high school in the 1950s.