dear boss：
i feel sorry to say i have to quit this job from you because i have to prepare for the graduate school entrance exam. i really feel sorry that i can't share with you some difficulties about the future plans of this company. it is not without a heavy heart that i think leaving the necessary job and great boss that i have been privileged to encounter during my thses days here. in the meantime, i’d like to express my deep thanks to you.wish our company has a continued success.
xxx
20xx.xx.xx