Event Module functionality

Hi Friends
i have one website where Teachers create events for their students
i am able to create Events with the help of Event module but the problem is
Events created by Teacher is not coming on Group Calander
Like there is a teacher of Mathematics and he is having a group known as Maths and there are 5 students who are member of this group
So whenever Maths Teacher creates event it must appear on group's calander and group members calanders but it will not appear even on Maths Teacher's calander
plz tell me why this is happening
and guide me towards solution