G'day folks,

i'd like to ask for suggestions for my problem here :
i have a netbsd 1.5 which is used for lab courses.
there are several lab courses, for example:
1.      algorithms
2.      database_programming

and i've got students in my server as follows :
username        group           courses taken
rot             student         algorithms
dummy           student         database_programming
brainy          student         algorithms, database_programming
guru            teacher

i want all students *not to share* their works with one
another and make
sure the teachers
can access the students' work in their home directory.

i come up with a solution like this :
* change students' directory permission to 750
* change owner of students' directories to teacher
(freebsd keeps telling me that the owner of the
directory doesn't belong to the owner)
* blocking chmod (but sometimes the students use this)

i'm sure better solutions exist.

thanks in advance,
roby