ugh. Maybe the teacher could use a thesaurus. I don't think it's appropriate for her to behavior anyone's behavior as "perfect." Perhaps, after you explain that your son and others have issues with perfectionism (and he is very aware of the label with the white cards) you could suggest something else, like:

excellent, fabulous, grand, great, marvelous, superb, superior, superlative, terrific, top, top-notch