I agree, talk to the teacher. I think a change of seats would be far less upsetting for her than a change of class. The teacher may also find a way to "work with" the competition if you know what I mean - give stamps for the most accurate work or the most interesting idea, rather than for finishing fastest? I think the competitiveness is normal, and likely to continue with other students/classes, but could be handled better if the teacher was aware of your concerns.