If you have failed in the 12th board examination, then your school can't do anything. Its all dependent on the council and if you have failed then you have to reappear for the examination next year.

Now if you have failed in Mathematics in 11th standard, then your school may help you. But again, its dependent on your school, that either you are eligible or not the grace marks.

I would recommend you to contact your school/class teacher and get it discussed. The proper information regarding this question can be made by them only.

I hope this helps. Wish you a great day!