In Exchange 2007 is there a way to set Message Delivery Restrictions for an AD group?

I am running Exchange 2007 in a school. We don’t allow for students to send emails to each other or they use it as a messaging system and share homework and the school can pretty much become plagiarism central. So the way we deal with this to to make use of the Message Delivery Restrictions feature.

I know we can use the EMS cmdlet:
  Set-Mailbox -Identity “Jane Doe” -RejectMessagesFrom “All Students”
but this is only for the single user Jane Doe.

Is ther a way to set the rule for all the members of an AD group?