Stopping appointments been shared out

HI Guys

I'm working a t a school and were using Exchange 2010.

I have a users calander that we used to use as the whole school calander before we moved over to sharepoint .

I've removed any permiisons from his calander about sharing it with people but still everytime he recives a meeting request all the staff recive the same appointment its satrting to drive me mad any ideas would be much appreciated