This happens in other fields. Even for a Chinese Language text book for overseas puples/students, one instance is that they switched to another version (three years ago, not sure if it's the case in the states)which is more difficult for kids here, not mentioning for the few native kids ... it seems that they just wanted to frighten the kids out of this ... several that I know just dreaded going to Chinese language classes ... forutunately i didn't let this happen to my kids ...