Export brushes FROM ipad

I teach Photoshop classes in a mac classroom. Outside of class, some of my students use Photoshop on their ipads to complete assignments, which is great, except they can't turn in .abr brush files. I require this for some assignments, to assess that they can create custom brushes. How can they transfer brushes used on an ipad to the computer, so that they can turn that in with the assignment? If it's not possible to export brushes files from the ipad, can they save them to their Library and open them on a desktop in the classroom?

I find tons of resources for how to get brushes INTO the ipad, but none for how to export brushes OUT! I think this would be important for those working on both a mobile device and an imac.