How to prevent files from being uploaded to OwnCloud when accessed from a specific subnet?

Question

ownCloud/Nextcloud

How to prevent files from being uploaded to ownCloud when accessed from a specific network? Or vice versa - how to allow downloading files only from a certain one?
The essence of the problem: I am considering the issue of introducing students' information storage into the network of an educational organization. Access to your own storage from the educational organization without restrictions - i.e. upload and download, but the volume is maximum - 50-100Mb (this is enough for laboratories). Access from the external network - only for downloading these files (for example, in order to complete the laboratory on a home PC). Nothing can be downloaded back. He brings it back on a flash drive and copies the files through the teacher's PC (that is, the teacher controls) to pass the practice.
Restrictions:access to the Internet from educational computers - no (only at the request of the teacher), to LAN - yes. Flash drives on educational PCs are blocked, but there are network folders - for each classroom - its own.
Maybe someone faced a similar problem and found a solution besides ownCloud? Any suggestions will do.

Answer 1

Hm. The Internet suggested only a .htaccess ban on access to certain ownCloud URLs (or vice versa a ban on everything except those allowed)