I have never, however, used SecondLife for educational purposes.
On SecondLife, I've been known as Baptist Breguet. While I have always considered SecondLife as a learning experience, I've never considered it a learning experience like in a typical classroom.
I've done a lot of reading about this subject as of late - when I saw the original assignment, I had to swallow a grain of salt and realize that I'm not the smartest person in the world.
SecondLife is cool - don't get me wrong. I've just recently come to despise it once its grid became the Windlight grid - it slowed everything down, and I shuttered my house building business that had become somewhat profitable.
I digress - I found a great article that spoke to me in one simple sentence - "Virtually all college students have had experience with games. Games represent active, immersive learning environments where users integrate information to solve a problem." This is such a great thing to say - and a brilliant analogy. I've said it on many discussion boards - learning CAN and SHOULD be fun! SecondLife certainly crosses this bridge. Plus, putting a classroom behind a locked door in a building can make it great for an uninterrupted lesson - and even more "lifelike" if the participants have microphones.
SecondLife could (and I use that word cautiously) be the wave of the future in education - but they really need to work out all the connectivity issues and slowness to ensure that happens.