Board Thread:General Discussion/@comment-71.232.131.59-20131205143653/@comment-1387259-20140113030122
From Katawa Shoujo Wiki
It was stated in the game that a) students don't need to have a disability to enroll in Yamaku, b) Yamaku doesn't accept students with mental disabilities, and c) Misha is enrolled in Yamaku to better her skills in Sign Language, since she wants to be a teacher. While many fans have speculated that Misha might have some form of ADHD, as far as canon material is concerned, she has no revealed disability.