Original not given unless one month salary check is submitted

Dear Sir/Maam, I am currently working in an international school in hyderabad. I have received an admission for my MEd and am in need for an educational loan. I had approached the principal requesting for my original certificates. I was asked other originals or one month salary check. When I informed that I was unable to provide the above I was asked to provide a bank mail requesting the certificates. I have provided them with the mail. Now again I am being asked for a check for the release of my original certificates. When asked why this is the case, I am informed this is the school policy. However, I have not signed any statement mentioning the above clause. For this reason and a few more incidents of uninformed striping me of my designation and reducing pay obtained bed for the designation with no information, overburden ( extra classes given than which agreed upon when joining) with no pay hike (same pay for double the work) inspite of requesting for some relief since july and being spoken to insultingly for a leave I had taken as I was unwell, I do not feel safe in this working atmosphere and feel violated. Please guide me as to what I can do?