Given the expense of using telephone connections, I thought you might find the idea of doing Web 2.0 work offline useful.
I found this blog post about students and faculty working offline. It reviews one platform. This author also has a tag for other posts written on this topic.
Twenty years ago, the fifth grade teacher at my daughter's school introduced multi-media work to her class. She had 180 free minutes from Prodigy (web host). All student activities and reports for the year were done within that many minutes of connect time.