This depends entirely on the rules of the organization you pledged and possibly the school with which it is affiliated. Without that information (and I would not suggest you provide us that info), none of us knows anything.
Speaking in VERY general and possibly inapplicable terms to your situation, if you have pledged an organization, you have accepted their bid. They can terminate your pledge status in most cases without much ado, but with regard to GPA, most groups are going to worry about what your GPA is at the end of the semester, not at mid-term.
I can offer this advice, which is the best advice for your situation: Go to class, study.
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Mu Tau 5, Central Oklahoma