My take on this is that regardless of subject (elective or not) there are many ways to achieve a good grade. Attending class, doing homework, presentation/term paper, reading up on required skill, probably even chatting with a professor. Doing all these things to fullest, will normally be more than required. I assume doing homework and going to class will be be enough if done perfectly. If my sim is late for class he will do some of the other tasks - like read a bit more on the skill - to compensate. One sim got the wrong presentation board and could not give a presentation, but still achieved A+ in that subject, thanks to working a bit extra on skills (or maybe he was lucky already being well skilled).
I did not think that electives come with any other "rules" than the regular subjects, but are more like a good way to select a smart elective for variety, but also if your sim already has high skills in something that is not directly relevant to the chosen degree. Could make that term easier, if succeeded.