OK, as the "education supervisor" of a bunch of school aged kids who do not attend EdB registered schools in Hong Kong (1 child is PR, the others not yet), what happens with our bunch is that I have to submit twice-yearly reports to the EdB with details of the kids & their parents, what syllabus(es) they are following, timetables, and reports on academic progress.
There are teams assigned to follow up on "non-attendance" cases in all districts, and we fall in their remit. Occasionally our case officer might breeze by to check that we're doing what I say we are, or call a family in to show samples of the kids' work, but as we can Show Cause why these kids aren't in a regular school, the EdB doesn't hassle us unduly.
We did have one older student (junior high) studying with an online school, but it turned out to be a right royal pain, as the school would not produce sufficiently detailed reports - or at the right times of year - for the EdB case officer. That student was then assigned by the EdB to an EMI aided school in our district.