Choi simply took over the Ivy College professorship that Palmer had had IIRC.
As pointed out above it was actually Millar who used the Atom like that. With cute ideas like Ray leaving the answers to the end of year exams lying open on his desk. A desk he had shrunk down to a subatomic size. Any student could read the results, s/he just had to work out HOW. And any student who could do it, got an automatic pass anyway! :D