Sri Chaitanya Techno School — Regarding sibling concession issue

Address:

Sri Chaitanya Techno School, New Town, Kolkata

My two son Reyansh Sharma(Class-II) and Devansh Sharma(Class-I) study in Sri Chaitanya Techno School.
10% sibling concession was told to me and according fees were taken and allowed to sit in the exam. But now they are showing that 10% as dues for previous year and wards are officially not promoted. However the school had taken the fees for this year as advance and allowed provisionally to sit in higher class and assured me that they will settle the matter.
But till now they had not solved the issue and my son will not be allowed to sit in the exams.
I have perused the matter but no response till date