This one sure is a head-scratcher, ain't it? On one hand, I agree that the dog should be allowed in the classroom to do his job. On the other hand, I also agree that the other children need to be considered too. My wife is a grade-school teacher and can't have classroom pets because every year there is someone who is allergic to anything with fur; hence me ending up with numurous "critters" at home that didn't last in the classroom.
And yes, I have forbid her from getting any more pets. The zoo is closed.