You are an administrator and you know that a teacher in your department is going to leave in the middle of the spring semester to have a baby. The subject terminates in a brand new regents exam.
Hire an inexperienced substitute to take over the class while the teacher is out on maternity leave?
Give the class to an experienced teacher before the new semester begins so the students can have continuity for the entire term? (Incidentally, these are the weakest students in that particular subject.)
Big decision--aren't you glad you are not the administrator making the decision?