I have not taught, but learned piano over Skype, I moved away from my teacher and carried on for a time via Skype. (Oh, I wonder if I was one of the favorites?
Hehe)
As far as Skype, it largely depends on what sort of access to technology you both have, how tech savvy you are, and network conditions between you. I can't recall ever making a call to India, but frequently to China (from the US) for business and sometimes it was crystal clear, sometimes it was unusable. I sometimes would use GMail or Discord's video streaming service, but in general they all seemed to suffer the same condition.
The teaching seemed nearly as effective as when I was in person, although I would much prefer to have lessons in person.
Topic: Teaching Piano... on Skype!