Access denied even access control set to "allow to edit"

I have a group of users called "students".

In access control, I set "studentss" to be able to create AND edit his own Pages.

The problem is:

If an internal member creates a page, he can edit this page normally;

HOWEVER,

If somebody else, eg: an admin, creates a page and then set author to be a user from "students" group, then the author cannot edit his page, always gets "Access denied" error.

I have "Node Access" module installed and I think it is because of Nodeaccess module because everything works properly before.

In admin/user/nodeaccess, I have enabled "students" to view, edit, delete Pages.

Any idea why?

Thanks,