Unfortunately, with the current (latest as of today) iOS software (4.2), you can't view the entire app via the iPad's VGA adapter. You *CAN* see the videos projected via the adapter. But, the rest of the app will not be projected.
This feature is something that we'd like to get right in the future. And, it was demo'd on the new iPad 2. So, hopefully it will be coming in the future. I know that's not optimal for you today, however. Sorry about that.
We are thrilled that you want to use it in your classroom. Hopefully we can make it easier for you in the future.