Many of the top MBA programs require a letter from an applicant’s It would be obnoxious in the extreme for a manager to object to writing one due to “I’m too busy”. I have (only a few times) refused because I wouldn’t have been able to come up with a positive endorsement (and then I usually say, “I think there are other people you’ve worked for who can write a more enthusiastic letter”). But to claim you are too busy when an employee wants to go back to school? That seems mean.