Sub: Resignation from the post of ____________
Dear Sir,
I request you to kindly accept my resignation from the post of _______in your ______.  Please treat this letter as the one month notice I need to give to resign from the post, effective from _________.
I wish to pursue further studies and improve my qualifications to enable me to have better career prospects.  I have recently qualified in the entrance exams for __________ and I wish to pursue it.
I shall be only too glad to complete any other formalities which are required from my end.  I also request you to let me know about the handing over of my Charge and other things in my custody.
Thanking You,
Sincerely,