White kid is sitting in black kid’s assigned seat. Prof doesn’t want to dislodge white kid, so when black kid asks if he can sit elsewhere, prof agrees. Another white kid in a seat that is closer to the front leaves, so prof asks black kid to move to the newly vacated seat.
But by now, black kid is unpacked, plugged in, and taking notes, so he says no. And yes, I’m sure he was somewhat resentful that a white student in the wrong seat was not asked to move, while he, the black student who accommodated the mis-seated white student was.
If this doesn’t seem suspiciously like racism to you, I don’t know if anything would.