For Academic year 2022-23 there is no such guidelines for individual registration.
This was only valid for year 2021-22 due to covid 19 . So, you can only register through your school.
It would be better to form group of students and reach to school authority to put your demand and request for the same.
If any school doesn't conduct such an intellectual exams , it shows their irresponsible attitude. Shame on them as they are not schools but money-making machine.
The main aim of SOF is to train and enhance developing brains to harness hidden power of students which will indirectly benefit mankind and Nature.
Anyway, You always have options you can participate in other Olympiad like Unified council Olympiad, NTSE.