I'm working for a school and got an opportunity

The service agreement or Bond was drafted in lieu of what extar ordinary benefit by employer to you? 

Say some training from some Instt that would add to your qualification?

What is your designation and nature of duties?

Without seeing the bond/ agreement, it is kind of difficult ot advice. However, broadly speaking, bonds and agreements are invalid and cannot bind you to an employer. If any employer has spent money on providing you some extra training/ facilities, then they are allowed to recover the money through such bonds/ agreements and nothing more. 

BoNDS  AND AGREEMENTS WHICH  ARE ONEROUS HAVE NOT  MUCH    LEGAL VALIDITY.iF THE AMOUNT OF BONDS IS REASONABLE ONLY THEY ARE VALI.D iF THEY ARE EXHORBITNT THEY ARE NOT VALID.sAME WITH TERMS AND CONDITIONS OF BONDS WHICH A RE ONEROUS. . TAKE UP fOREIGN JOB AND DON'T GET COWED DOWN BY YOU RPREVIOUS EMPLOYER THREATS OR INTIMADATORY TACTICS. WHETHER YOU  GET YOUR SALARY OR NOT YOU LEAVE IT ASIDE. iN YOUR  OVERSEAS JOB YOU MAY GET MUCH MORE SALALRY.ENQUIRE WITH YOUR NEW EMPLOYER WHEHER WITHOUT SERVICE CERTIFICATE AND RELIVING ORDERS YOU CAN JOIN THEIR  COMPANY.iF YOU APPRECIATE THIS ANSWER PLEASE GIVE ME ALL MY  PROFILE LIKES.

Do not compromise on clean releiving and proepr relieving docs.

Submit notice of resignation  (dated as communicated by you in office) under proper acknowledgment.

Is there any education tribunal in your stae?