You guys don't understand Kaiba's sensabilities. To him, if you're a duelist, you belong in a super-elite club. But it wouldn't be awesome enough if it was somewhere comfortable and safe; to become a real duelists, you have to become a superior man who can laugh at danger, etc.
Also, Kaibi tends to project his ego. He would view the most pathetic loser in the school as being an ultimate superman duelist able to fuck-pwn any duelist from outside no matter what -- because it's HIS school.