Sean Aldridge, 37, a former teacher at Warblington School in Havant, Hampshire, was found guilty of 24 counts of sexual activity with a child. He has been jailed for 12 years.
Aldridge had previously been investigated by the school but was subsequently promoted to assistant head teacher and head of safeguarding.
During the three-week trial, Portsmouth Crown Court heard that Aldridge, from Southsea, had sex with girls aged 13 to 16 between 2006 and 2012 on school premises and in his car.
One of his victims became pregnant before suffering a miscarriage, the court was told.
At his sentencing, one of his victims read out a statement saying Aldridge initially made her feel special but she was left feeling "dirty, used, stupid and embarrassed" after he took her virginity.
Passing sentence, Judge Roger Etherington said of Aldridge: "The abuse of trust was truly appalling. You were perceived as a good or outstanding teacher with a special rapport with pupils."
He said it was "quite extraordinary" that by 2017 Aldridge had been made the school's safeguarding lead, a post he said would have taken "breathtaking arrogance" to apply for.
A Hampshire County Council spokesperson said the school took "immediate action" when it was informed by police of the allegations in 2017 by asking Aldridge to stay absent from work during the investigation.
The spokesperson added: "While the county council is unable to comment on the reasons for the individual's changes in position and role at the school, which are matters for local school decision makers, it should be noted that all of the relevant checks were carried out on this employee."
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