Mewing with braces, problems

I heard mewing only works with braces that push the teeth outwards and not inwards. Now in my case, I wasn't able to get all the information I need because of my parents. I only know that the teeth on my lower jaw are being pushed outwards, does that mean that the teeth on the upper jaw are being pushed outwards as well? Or could they be pushed inwards? I do wanna see results with mewing so a quick respose would be helpful, thanks.