I caught two kids cheating and I’m not sure what to do about them because they deny it

Two of the kids in my class are best friends and there is photographic evidence that they cheated off each other. They both deny cheating though and say they did it by accident, and the other deeps in denial says she’s been getting the same grade all semester so it doesn’t make sense for her to cheat now.<br><br>The evidence I have is pretty concrete, but they are still denying it. You can literally see one of their pencils moving and it is pointed at the other persons test. I’m just wondering what to do in this situation because they completely deny it.