As an adult who has issues with perfectionism herself, a mother who does, and a child that shows signs of it, I'd be first on the train to the teacher or the principal to get that word changed NOW! Talk about setting up a track early for failure and for kids to have low self-esteem!!!! Excellent is one thing, but using perfect is completely different! It's like telling children, even those who aren't perfectionists, "you are not good enough" before they have even had a chance to try or learn or attempt to accomplish something!!!!
Personally I think that word alone is part of the reason there are so many issues in this world - divorce because a relationship is not perfect, stress because income isn't perfect, greed/keeping up with the jones's because a house size or tv size isn't perfect, those that push their children too hard and don't let them be kids too because they aren't the perfect student or perfect athlete or perfect singer, etc...
The only time I use the word perfect is to describe something that my children give me (i.e., a drawing). It is perfect because it has come from their hearts!