Turnbull, you're guessing??!!! You, who have seen this movie 2,000 times (legend has it ) and know all the dialogue by heart? Can it be that you have forgotten the conversation in the GF2 flashback scene? It proves that you are correct and that you need not resort to guessing: Michael did indeed attend college after leaving high school. He must have enrolled in the fall of 1938; and we definitely know that he dropped out in December of 1941 to enlist in the Marines after the attack on Pearl Harbour, as per the following exchange with Sonny:
Well, I know Turnbull that you are only human and you're allowed to forget a line or two from GF once in a while . You need to have other things on your mind, after all. Wait -- I know what happened. When you said you were guessing, you were referring to guessing about the time line of the book, not the movie. Well anyway, you were right .

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If so, he could have met Kay at any time during those years before Pearl Harbor.

Now there, I don't think you're correct.

After Michael was discharged from the Marines, I believe he returned to Dartmouth to complete his education, and I think that's when he met Kay. Like plawrence, I also got the impression that they were both students there.

On Geoff\'s main Godfather[/i] web site , the page [i]Godfather Family Portraits indicates that Kay is seven years younger than Michael (although the page Corleone Family Timeline indicates that she is only four years his junior). Either way, as SC said, she would have been too young to have been enrolled in college when Michael was attending the first time {pre-Pearl Harbour). But by the time Michael re-enrolled, she would also have been a student.