I don't think that that is the case, so much, anymore.
Basically, you'd better be pretty awesome, like an astronaut or something, and someone who wants to get theirs hands-on with a chapter. And self-recommending is not a good way to go.

Isn't is actually true, that in most NIC and NPC do not take Grad Students?

Not to start a wee weeing contest, there is a difference between Social, and other Special Groups who use Greek Letters.

The Divine 9 also have their own structure so they do theirs differently.

Then, how long a go was this post started?;)

My sister Betas have already weighed in on this, but we accept members regardless of collegiate standing. I'm an alumna of 24 years and enjoy my active status in BSP.

From what I understand, Beta Sigma Phi is not a collegiate-based sorority, and is not an NPC group. We have 3 Beta Sigma Phi chapters in my town, and the only college we're near is a junior college. And the chapter members tend to be in their 30s and up...WAY up.