Further concerns were raised about child safeguarding at missing teen's Megan Stammers school after it emerged that a former teacher was jailed for grooming a pupil in what a judge labelled a "grave breach of trust".
In 2009, a teacher at Bishop Bell C of E School was jailed for seven years after grooming two pupils on social networking site Bebo.
Robert Healy, then aged 27, had sex three or four times with one teenage victim after taking her back to his father's house over a period of a fortnight.
Megan Stammers' parents were visibly upset as they appealed for their daughter to return
He then started a second relationship with a slightly older girl from the same school, where he was a supply teacher.
Separately retired Church of England priest Canon Gordon Rideout, who faces child sex charges, is a former chairman of the governors. The 73-year-old is accused of committing 38 offences over an 11-year period at Bishop Bell C of E School between 1962 and 1973.
He was charged in June following a nine-month inquiry by Sussex Police into allegations of child sex abuse in the 1960s and early 1970s.
Rideout, from Polegate, near Eastbourne, has been bailed to appear at a plea and case management hearing at Lewes Crown Court next month.
The school has previously said that he had links to the school but was not a member of staff and that the allegations were historical and unrelated to the school.
Speaking about the disappearance of Megan, Jon Bird, acting operations manager at the National Association for People Abused in Childhood, said: "We would say that the board of governors and the headteacher need to co-operate with police fully."
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