I am not sure about 1961, but In 1962 the Fall Quarter at the University of Washington did not begin until the last week of September or the first week in October. (I didn’t attend, but my friends did.) I registered for evening classes for the Fall of 1964 during the last week of September and I don’t think they began until Oct 1. It was not difficult to register for night school—and you could drop classes without a penalty until mid-November. I dropped Organic Chem when the curve kept dropping out below me. I did not receive a permanent student number until I registered for regular classes in the Fall of 1965. My point is that registering for night school did not imply any immediate time commitment. I had a full time job.
I went to NYU in 1961. In those days most colleges used the old (unmodified) semester system. In that system there was a long Christmas thru New Year's holiday, followed by the last couple of weeks of class and semester finals near the end of January. Since that time most schools not on the quarter system use the new (modified) semester system, starting before Labor Day, with finals ending before Christmas, followed by a long inter-semester break.
I'm a little confused, did you or did you not, at least theoretically, need to start attending class in late September or around the first of October?
I do tend to think, based on the image of the transcript, your statement, and an investigation of class start dates at U. Washington going back to 2000, that the classes started 9/19/61, not 8/19/61.
However that still doesn't give Stanley Ann much time to recover from the birth, a few days at least, get plane reservations, pack for Seattle, find housing, find a babysitter for the times/days the two classes met, and otherwise get settled. Do-able, but pushing it. Now, if she already had decided on attending, already had a place to live, plane reservations, etc, (or was already in the general area, but not at the University yet, before BHO was born, and only needed to find a babysitter, that would have made it a piece of cake.
Reports from one of her friends puts her and Baby Barry in the Seattle area in mid to late August of '61, with her not really not knowing how to change his diapers. (No trivial thing to learn for an only child in '61, no pampers in those days, just cloth, plastic pants, and diaper pins.).