My kid got this from school, in South Korea. The leaves are about 3 inches long and are thick and stiff.
One leaf has fallen off and I re-potted it, but I don't know how to care for it or what to expect. It seems to be doing nothing at all.
I am going to guess and say it looks like a non variegated Peperomia clusiifolia, or it could be Peperomia claviformis. I can't decide.
Peperomia-Clusiifolia
Peperomia claviformis