Good again:
I did not find the way of preventing a created user from having a personal assigned space with owner rol, but I achieved that the teacher and the pupil were sharing the same space with different permissions.
It is true that when I create a user with the wizard, grants to the above mentioned user total permissions, owner, of his /her personal space.
What I do, is that I have a space dedicated to it for all the users that I am creating, and then I modify the path to his/her personal space, and remove the permissions from him/her in the initial folder.
Regards,