Having said all of that, Second Life, as is, is not a teaching tool. It is content free. It is closer to a virtual classroom tool, or even a real-world meeting room or water cooler (without the actual water). Any content has to either bubble up from spontaneous conversations (great when they happen, but not predictable or scalable enough to provide an intellectual payoff), or be "brought in."
Ummm ... but aren't virtual classroom tools or meeting room tools a "teaching tool" if used correctly? And, if you are able to enhance these with persistent content, doesn't that become a teaching tool.
How about the ability to fly around the solar system? Could you maybe learn about the solar system that way? That's in there?
I think maybe Clark is more worried about distinquishing something from something:
mostly, I worry that educational simulations will be lumped together with Second Life
Not sure the point he's making. If someone scripts a simulation in Second Life, does that not count or something?
No matter what Clark says - Second Life is a teaching tool.
I personally believe that the next generation of Second Life that gets around some of the current technical issues and provides presence audio is going to have adoption patterns similar to virtual classroom / virtual meeting tools.