Can you have metal braces on top and Invisalign on lower teeth?

Just curious. I don't have to get lower braces for another nine months, but, for both aesthetic and curiosity's sake, would that be allowed? Metal braces on top teeth and Invisalign on the bottom, so I could compare the two and potentially recommend the options to friends? The top ones, I had two teeth pulled and have to bring two baby teeth in, but my lower ones are just slightly crooked on one side. I was just wondering if this could even be an option.