Andrew Riley, former head of sixth form at Baines School, was due to hear the result of disciplinary action last Monday afternoon.
But the 38-year-old handed in his resignation hours before the 5pm school hearing.
Despite Riley's decision to quit, his case will now be reviewed by the General Teaching Council (GTC) which will make a decision as to whether he is fit to continue teaching.
In a statement, Roddy McCowan, headteacher of the school said: "On Monday the board of governors accepted Mr Riley's resignation, which he submitted in writing before the disciplinary hearing.
"I would like to thank pupils, parents, staff and governors for their help, loyalty and support throughout this difficult period at Baines School."
Married father-of -two Mr Riley was last year cleared of two charges of abuse of trust, namely having sexual relations with a student in his care, and one charge of offering to supply cocaine.
At the two-week trial at Preston Crown Court he confessed he planned to sleep with the then 17-year-old student, but claimed guilt over what he was doing to his family always stopped him.
Although he was cleared, Mr Riley, who lives in Lancaster, was suspended on full pay as the school launched its own investigation.
After the verdict of the trial, the student involved in the allegations spoke out, saying she believed he should never teach again. She also warned other girls against acting on their feelings for teachers.
A spokeswoman for Lancashire County Council, which governs education in Wyre, confirmed the case would now be reviewed by the GTC.