Event or Ad-hoc message to whole school or any year group

Ross, Is there a way to publish a ad-hoc message (like school will be closed tomorrow OR Special school event tomorrow) in gibbon for the whole school, or only to a specific Year group, so that if any user open a site, get this ad-hoc message and prepare accordingly.
Will be also useful for any major event in the school.

Thanks
Rakesh

Hi Ross,
Got the solution again. Messaging module is very flexible and covered all the requirement. We are trying to set the Email and SMS option now. will see how it goes. Hope that will also be not so difficult.
Regards,
Rakesh