Hi Maggie,
If you and your students don't want the email notifications, you guys should unsubscribe from that forum. You can change the subscription by visiting this page:
http://n2.nabble.com/user/UserSubscriptions.jtpYou can also click on "Options > Users > Manage subscribers" to remove your students.
I think you should have a sub-forum called "Annoucements" and only you should post there. Then your students should subscribe to that forum to know when there is something new on the forum.
Please let us know if this solves your problem.
Regards,
Hugo Teixeira
Nabble.com