Disaaproved Appointment by the Civil Service

Good Day, I am Aj from Davao. Last July, I was Hired as a Teacher in a Government School wherein later did I know that the Job Posting didn't match with my educational requirements. I was hired as teacher 1 whereas the schools job posting was teacher II. The civil service denied my appointment, but the school later appealed to the regional office to reconsider my appointment. Then it was denied again. I filed a resignation letter to our head because I feel that I am really not qualified for the Job of teacher II.
My Questions are these and I do hope you can help me;

1. Can the school do anything to prevent my resignation?
2. I have been given a salary, will I be forced to return it?

Hope you can help me. Because I have been offered a job of a permanent status.

i don't think you can be compelled to continue, but your appointment was considered valid until it was disapproved so you shouldn't have to give back salary for work already performed.

attyLLL thank you po, I have tendered my resignation na po and I will be out January 31 2013 Po, but our head has not talked to me yet, I am just waiting to be called.