First of all, please forgive my poor english, I'll do my best :-)

I'm a teacher and my students have to give lectures themselves, and I have to evaluate the lectures of some of my students. Other students are evaluated by other teachers.

First of all, students would put their lectures schedule on the web, and they would be able to modify their own schedule. Of course, students aren't not supposed to see the schedule of other students.

But me, as I'm the teacher ;-), I should be able to see the schedule of every student, and I would like to display on the SAME calendar the schedules of some of my students (which should be chosen in a list).

My aim is to see instantly the schedules of all the students I'm supposed to see and evaluate to organize my trip to student's schools. I hope that it is (nearly) comprehensible...

Is it possible with Zimbra ?

I'm only interested in Zimbra for this usage... I don't care about email and so on.
Is it possible to hide everything for my students but show them only the calendar module ??

Or maybe is there an other (free) shared calendar I could use for this usage ?

Thank you very much for your help and your advices !

Best regards,