Surely at the beginning of recruitment you'll receive information regarding the GPA requirements for each specific sorority. When you meet your recruitment counsellor, you can ask her about it too. If XYZ sorority wants a 2.5, and you only have a 2.43, well then you'll just have to accept that you will probably be cut.
When you say that you're concerned about being cut due to your "age", that depends on how old you are, your class standing, and the recruitment culture at your specific university.
If you're passing on the grades issue, then just reiterate to the ladies who rush you that you're going to be around for a while. If they ask you about your class standing, you can say something like, "I'm a junior on paper, but I still have two and a half years left until graduation. I'm eager to make the most of my sorority experience during that time" or something like that.
Just go for it; you never know what will happen!
.....Kelly
Hybrid Mode
