Harry Potter for Kinect

Blackboard games are unlocked by completing the storyline sections of the game. I 5 starred each section as I went so I do not know for sure if it is strictly story progression that unlocks the games or if there is a required number of stars in a section to unlock each game. After you complete a storyline section it will list what you have unlocked.

After completing the entire storyline with 5 stars I hadn't unlocked this achievement yet. Once I started the Blackboard Dodging games completing each difficulty unlocked the next highest difficulty. This achievement unlocked when I completed Hard Dodging which unlocked the final Dodging game, Extreme.