The head teacher of Swan Valley Community School has left to seek new challenges.
Nigel Jones departed on Monday following a governors’ breakfast meeting called the previous night.
He was principal-designate for the school when it becomes an academy this school year.
A KCC spokesman said: “The timing is unusual, but he has other interests in education.”
He is succeeded by Alison Collwell who becomes acting head teacher.
Mr Jones was described by Ofsted inspectors on their last visit as “passionate about getting the best” from his 636 students.
He had raised Swan Valley from the doldrums after parents’ criticisms and concerns at previous Ofsted inspections.
Following Monday’s meeting a letter was issued to parents by Mr Jones and the chairman of the school governors.
Governor David Mote said: “I have no idea why he has gone, but he will a very difficult act to replace.
“He was an exemplary character. I am absolutely gob-smacked he is going.”
The school was the first to be built as a public/private finance initiative (PFI).
The school was built to provide the community with a library, nursery and meeting rooms.