> Teach the concepts, then teach a better, more efficient way of doing things.

You just stated why they don't want them in elementary school.

Also, it's hardly punishment to teach young kids why they arrive at certain answers. The calculator skips the steps, so you're doing them a disservice in the long run to not "punish" them. It's going to be a much harsher punishment trying to understand later on because math is really unforgiving to that. The greatest problem in math is generally that the students don't follow out of lacking understanding in preceding courses.