There is a good chance that you have seen Xtranormal Animations at some point. The website has been around for a few years now and enables users to use text to speech to create unique animations. It has been popular with many educators but previous lack of privacy controls made it less than ideal for many classrooms.
The company has clearly recognized this and has created an education version of its popular site with affordable pricing for schools.
If you enjoy getting your students to express themselves through animation, Xtranormal is worth taking a look at.