NOT A TEACHER
(1) Thank you for your note.
(2) I do not have the confidence to answer your question, so -- according to the
rules here at usingenglish.com -- I must not answer it. We will have to wait for a
teacher's answer (or the answer from a more intelligent non-teacher than I).
ostap, once again you are pushing things to extremes. In order to create a context for this utterance, you have come up with this:
You have a coworker. You don't know whether he graduated from college or not - indeed, so far you have not told us that you know for a fact he has even attended college (though no doubt you will). For some reason or other you feel the need to tell a third party that your colleague was/has been a good student at college.
I suggest that if you knew that he was/has been a good student, then you'd know whether he graduated or was still at college.