I highly recommend you take a look at Wiziq for online synchronous learning.
Mark
WiZiQ is an online teaching platform, which provides a free virtual classroom environment for teachers to interact online and teach students in real time. Teachers can also build a profile, keep an availability schedule, and maintain a content library, which is associated with their profiles, by uploading PowerPoint presentations and PDF Files.
I can tell you many many language teachers love Wiziq. Spanish, Chinese, English, etc. That's why I thought Latin and Greek teachers would enjoy using wiziq.