Don't worry about him taking oral exams in college! I think that was completely wrong for the teacher to say something like that to you. He has been in school for a month or so now right? Is he bored? Sometime smart kids get bored and start doing poorly in school. If he picks up on things quickly he may get bored having to repeat them on paper. Try to find fun new ways to work on his written work at home.
I assume that in Kindergarten he is not writing papers, mainly working on letters and numbers? Writing simple words, drawing shapes, etc. Try smearing shaving cream or whipped cream on your kitchen cabinet or table (a surface it will not ruin). And have him try his written assignments by tracing them in the shaving cream. It is more fun this way!
You can have him write with playdough, make snakes and have him turn them into letters and shapes.
Make sugar cookies in different shapes and decorate them or write on them with icing.
If he can do things in these fun ways, you know he does not have a major problem, he just needs a more creative outlet.