@Gor***
, Then when you have 45 days or less left on that stamp you will need to take paperwork from your school to the immigration office and apply for a yearly extension of stay based on employment.
Once they issue you a yearly extension of stay, they'll staple a paper into your passport stating when your 90 day report is due.
You don't need to do anything about a 90 day reporting until you get your yearly extension of stay.