I'm having the students write a new function for the kernel as part of an exercise. We can't seem to determine what the magic is to get the newly created function into the symbol map so windbg has it.
I thought I would answer my own question.
It turns out the file I was modifying is used as part of a library that was then linked into the kernel. The function I was adding was orphaned for now, and thus it was not included into the fully linked kernel.