how to connect two ipads with bluetooth

iPads cannot pair to each other, but if the App requires a connection its up to it to create it without requiring it to pair.

So whatever you need to do for the Apps to work should be done through the App. Follow the up instructions to connect them.

Pairing cannot be done nor should it be necessary.

You cannot.

Pearson educational sells an app (for iq testing) that relies on two iPads being able to connect via Bluetooth... Why can't two iPads talk via Bluetooth?

Why do you want to connect two iPads via Bluetooth? If you want to share content wirelessly, you can make use of AirDrop (running iOS 7 or later)