I would keep a notebook next to the computer. If they do a lesson and nothing is written down/no work is shown, I would make them redo the lesson. No moving on until the work is shown. At least make them go back and repeat the problems they had wrong and show their work on those. You are still the teacher and the mom. If they were in school and the teacher said she needed to see their work and they didn't show their work, it would be marked wrong. My kids are not quite teenagers though, so maybe this is just wishful thinking.