Hi Alex,
Here are some thoughts.
The key to the project is that each student has one or more parents/guardians (I'll call them guardians from here forward to be inclusive). The Guardians are the actual users of the system. OACS tends to represent such things using groups.
Thus each student should really be a group; perhaps a user with an associated group, but definitely a group. A group can be made a member of another group. Thus rather than, or in addition to, making each student a member of a class you can fairly easily modify the code to make the student's group a member of the group. I think you will want to use Composite relations here.
Are you going to be using Oracle or Postgres? Open Force wrote a package for Sloan that allows the creation of Personal Communities for each dotLRN user. Its oracle-only and has never been used in production, thus might have bugs and definitely needs UI work and it has not been documented. However, it might be exactly what you want. It would allow each student to have their own community where teachers could upload progress reports, photos whatever. This could be reused from session to session forming a permanent place for records on that student. I expect this package will eventually become the basis of portfolio functionality in dotLRN.
Here are some pointers to the docs on groups etc.
https://openacs.org/doc/openacs-4/groups-design.html
https://openacs.org/doc/openacs-4/permissions.html
https://openacs.org/doc/openacs-4/parties.html
https://openacs.org/doc/openacs-4/permissions-tediously-explained.html
