Absolutely beautiful!
You and your students should be proud of this, as it was definitely an amazing piece of work. While there was little story provided (who were these 2 characters? Why a giant castle? And who was the guy at the end?), I could forgive that because it enthralled me, making me want to see more. The fluid animation, and also the style of the artwork reminded me of something that would feel right at home in Disney's "Fantasia".
Seriously, awesome work!