Perhaps you could investigate the system which you are using to post the e-folios more closely, so that you can understand the encryption that they use, the security they have put in place to prevent general access, etc. Some questions regarding whether or not e-folio work was isolated from the general traffic of the internet would probably also help allay their fears.
I previously worked for a school district which required its students to post their work to an e-folio site. Each student had a login, and each teacher had a login, as did administrators. As far as I know, the information was kept intra-site, and was not released onto the internet. I know access for teachers was limited only to those students which were in your homeroom. Most sites are quite well-protected, as they open themselves up to liability should harm come to a child as a result of information being leaked.
Hope that helps.