It sounds exceptionally unusual to me... How are they going to pass him through year 10 if he hasn't been attending classes for the required time? How will they expect him to keep up with workload for the second half of the year whilst learning the first semester study load as well? He will miss his mid-year year 10 exams, which do count to final grades...

I would be seriously thinking about what BG has suggested, that this will simply be a way to get him 18 months of year 10, not passing year 9 and 10 in one year. I just cannot fathom how it would even be possible, especially given his issues already last year, he isn't an exceptional student, and not even the most exceptional are allowed to miss half a year and still pass year 10.