Recommendation letters for "good enough" students I'm a math professor. I get asked to write a number of recommendation letters to graduate schools where my honest view of the candidate is "this student would fall somewhere in the bottom 25-50% of their student body. I expect there will be dozens of applicants of similar quality and I have no  reason to favor this one except that I have a good personal relationship with him or her." 

Logically, this candidate deserves to go as much as any of the dozen similar people in the pool, but I feel that a letter which said the above would be a real disservice to them. Should I refuse to write them?  Describe their accomplishments and pointedly ignore that (if my estimates are right) they don't particularly make them stand out?
I've only been a student, so take this with a grain of salt. 

Be honest to them about their abilities and your perception of them before you write a letter for them. Grad school is not a small commitment. See my answer here also, for an answer to a related question. An excerpt which I feel is very relevant:


  Be very honest. You have information that they don't have that will
  be useful for them. I would rather you tell them what you know and have
  them make the decision for themselves, rather than let them keep doing
  what they're doing and seeing them fail.