Would you ground your child for a year? Even for bad grades? A semester is like a year for a college student. That is not a healthy way to do it.
When you talk about negative feedback or punishment it needs to be specific and immediate to work. That is why spanking works, but its not PC. And spanking your chapter members would start the most
peculiar rumours about your chapter . . . especially a sorority.
Anyway, chapter attention is the biggest thing (shame) . When things are not announced publicly (even if most people privately know) the problem can be ignored. So putting someone on the spot at a meeting is the best bet.
However, shame needs to be used intellegently, not in anger, and with a consistant process.
So a process would be to define the problems and their consequences in advance to the whole chapter. Preferably in the beginning of the year.
Then you would have people tracking the major issues such as academics or whatever.
Then when a situation comes to your attention you write a Letter of Suggestion. A positive letter of suggestion outlines a few clear and simple steps that the chapter will help with to improve the situation.
These type of things should be written in advance so they are ready, but then tailored to the individual brother. Nothing is worse than getting a purely form letter from your own chapter . . . I mean how silly is that? Even for dues.
You follow this up with a meeting to schedule these things . . . you give him a counselor to help him (and follow his progress).
And then if you are still not getting anywhere, and the situation is one that should be addressed you use chapter shame . . but again the steps should be so logical he (and everyone else) knows its coming.
Make sure there are some humanity checks in there! If a brother is under unusual circumstances you might want to cut him some slack.
Also, some stuff works well with some informal meetings, a suggested plan, and follow-up. But you need to document a synopsis of it in case a situation ever needs to go to the judicial board.