Out side of a citywide job action, if your school does not have money to pay for you, you are excessed. You still work for the department of Ed, but you are not assigned to the school.
There is no loss of pay or seniority. You are placed in another school first by district, then by borough.
If there is a city wide job action (layoff, it is seniority by license area). If you are a GC with low seniority, then you are laid off; your don’t get to jump back into your teaching license where you may have more seniority.